Nothing is perfect, including the Harbeth M40.2. Let me just mention the binding post issues I've had with each of the M40 speakers I've owned--the original M40, the M40.1, and now the M40.2. Actually this issue arose a while back with the M40.2, but I was too lazy to fix it immediately.
Unlike most speakers, Harbeths attach the speaker cable binding posts directly to a wood back panel. Most speakers, even cheap ones, have a binding post plate made of plastic or metal. And it's not that other manufacturers are cheaping out by refusing to give you a greater expanse of nice looking wood on the back.
The reason is that wood can expand and contract in thickness as the humidity changes. Most manufacturers choose to make the mechanical connections more or less permanently tight rather than go for ultimate woody aesthetics. Not Harbeth.
Thus, in my northern Midwest USA location, I noticed the binding posts loosening up midway during the first winter I had the speakers in my non-humidity-controlled home. I have baseboard hot water heat and no whole house humidifier. Thus, my listening room gets quite dry during the winter months, sucking the moisture right out of wood cabinetry, decreasing its thickness.
With decreased thickness, the binding posts, which I'm sure were nice and tight when manufactured in the relatively high humidity of Great Britain, started to loosen up. This is even though I don't use spade lugs or bare or tinned wire connections and thus don't put a lot of torque on the posts tightening them down on spade lugs or bare/tinned wires.
Yes, in the subsequent warmer times of year the posts tightened up a bit, but not fully.
How to fix? Well, you have to remove the back panel. And, unfortunately, with the M40.1 and M40.2, this operation is a lot easier to do if you turn the speaker cabinet upside down so that the binding posts are toward the top of the cabinet. But turning a large, heavy speaker upside down while it's on a stand is not an easy proposition and you will certainly lose the precision of your set up when you put the speakers back on the stand, necessitating another round of carefully adjusting your set up geometry, a process that can take hours, not to mention considerable muscling around of the speakers, especially when, like mine, the Ton Trager stands are mounted on carpet, sink into the carpet, and thus don't move around easily at all. Thus my "lazy" reluctance to fix this problem.
But once you choose to do it, the process is easy enough and takes less than 20 minutes per speaker. First lift the speaker off the stand and put it on a carpeted floor. Then turn the speaker upside down. Now use a #2 Phillips screwdriver to remove the 14 wood screws holding the back panel in place.
Once those screws are removed, pull gently outward on the binding posts and the back panel should start to pull away from the cabinet at that end. There is no reason to remove the panel completely from the rest of the cabinet. Just let the top of the back panel (the end nearest the binding posts in this upside-down orientation) rest against your chest and let the bottom of the panel stay nestle within the edge of the rest of the cabinet.
You will see the two binding posts inside. From the inside surface of the back panel there is a hex nut, a washer, the ring connector terminating the internal speaker wire, then a lock nut--in that order. The hex nut and lock nut are the same size so the same-sized wrench will work on both.
First, though, get a small screwdriver with a thin handle. Using the exterior binding post nut, lock the shaft of this screwdriver into the large-diameter hole in the exterior of the binding post, the one made to accept large-gauge bare wire.
Now find the correct size of short, miniature closed-end wrench so you can unscrew the lock nut. Hold onto the handle of the screwdriver you've locked into place. Then remove the lock nut on the inside, then remove the ring connector, and finally remove the washer. Holding onto the screwdriver handle will prevent the binding post from rotating and possibly damaging the speaker wire connection to the ring connector on the inside.
Now, use the screw driver handle to turn the binding post a bit (remember, it's already loose--the problem you are in the process of fixing) and orient that big hole so that the screw driver handle is aligned with the long dimension of the cabinet. So oriented, you've be able to insert wire into the big binding post hole from the top or bottom of the binding post, as things should be arranged.
Holding the binding post in that orientation with the screw driver handle, now use your wrench to tighten the hex nut against the inside surface of the wooden back panel. Don't be a gorilla. If you try that with this metal nut/wooden panel interface, you will either just dig the binding post into the outside of the cabinet, dig the hex nut into the inside of the wood back panel, break the post (it's largely hollowed out for that big hole, remember, so it isn't the strongest thing), or strip the edges off the hex nut. None of those are desirable outcomes.
You might be able to add an extra large washer between the hex nut and wooden panel on the inside, but the post is just long enough as is and the extra thickness of such a washer might not allow the lock nut to fully attach. Even if there is enough length, the outside part of the binding post then will be the part digging into the cabinet as you aggressively tighten the hex nut, the nice wood finished part. You don't want to do that. You could also add a washer to the outside of the cabinet to prevent the binding post from digging into the outside of the cabinet, but that washer will ruin the maximal-wood looks of the cabinet's back panel. And I'm pretty sure the post will not be long enough to accommodate the extra washers on both inside and outside.
Thus just tighten it snug; don't bear down with all your strength. That's one reason for my recommendation of using a short miniature closed end wrench. A short wrench--or, perhaps better yet, a screwdriver-handled nut driver with a deep socket--will help prevent you from over-torquing the hex nut.
Once the hex nut is snugged up, add the washer, the speaker wire's ring connector, then the lock nut. Make sure the speaker wire is oriented for maximum slack between its crossover connection point and the binding post--there isn't much slack in this wire, in my experience. As you tighten the lock nut, the ring connector will tend to rotate. Hold it in place with your finger to maintain its maximum slack orientation, then snug down the lock nut.
Finally, push the back panel back in flush with the cabinet edges and reattach the 14 wood screws, again not too tight because you will just strip them if you try to over-tighten them. You are just screwing into wood paneling, not metal.
Repeat the process for the other speaker. That's it; you're done.
Unfortunately, you really can't do this process right after delivery. It will take months of dry-climate exposure to loosen up the binding posts. But, once tightened up again, that fix should last for years.