It's good to store mangetic tapes as much unavailable from ANY external magnetic fields as it's possible.
Once I looked behind the curtains of german television during a technical study term.
Even the very small magnetic field of the earth is able to distort the mangetic tapes used for video recordings.
They have to be regularly copied every year or so to interrupt this effect, otherwise, the quality constantly degrades over the years.
The result will be a washed out like TV- picture, without any sharp contrasts and contours on the screen.
This happened to some tapes they forgot to copy in time and now they are literally lost.
Those time documents were only recorded by magnetic tapes, not parallel on film. It was done starting in the 1960's, when TV companies explored the great opportunities of magnetic recording instead of film recording (which always needs chemical process to deliver the pictures and has to be transferred physical to any destination in the country).
So try to shield your magnetic tapes from everything and never put electrical gear even in a location near them. It can hurt those tiny impulses and degrade them over time. I'm not talking about short periods here, but in the long run no professional archive will do it that way.
The magnetic master tapes of records are stored in a dry, humidity free, specific temperature and free of magnetic fields environment to stay fresh and healthy over decades.