🚀 go-pugleaf

Hello NeXT users!  I have a question that hopefully one of you kind people
can help me with.  What I am about to describe sounds completely insane,
but I have tried everything obvious and cannot find the cause.

I recently bought a modem and installed it on my NeXTStation Turbo Station
16/400.  To conserve desk space, I placed the sound box on top of the modem.
To my surprise, in about thirty minutes my machine COMPLETELY locked up---
it would accept NOTHING from the keyboard (even the command-command-~ and
alternate-alternate-* key sequences) and nothing from the mouse.  The only
thing I could do to get the computer to respond was press the "power" key,
but even then I couldn't hit the "turn it off" button because my mous wouldn't
work!  After calling NeXT support to no avail, I was forced to pull the plug
in a hard power-down.  To my surprise, WHEN THE MACHINE BOOTED UP IT WAS STILL
LOCKED!  I continued to power down again and again (four times total) until
finally I, by chance, removed the sound box from the top of the modem and 
placed it on the desk surface.  Then the reboot succeeded!!  After many trials
I determined that placing the modem on top of the modem somehow causes the
machine to lock up--trust me, I am a veteran NeXT user.

My question is this:  has anyone experienced this or a similar problem?
If not, can anyone hypothesize an explanation?

Since the top of the modem is moderately warm, I think that the sound box
may be overheating somehow, although this doesn't seem possible to me.

To repeat, it isn't the cables, slab, monitor, physical movement, or
ANYTHING ELSE which causes the failure---only placing the sound box
on top of the modem.

Any help would be greatly appreciated.

Thanks,
Dave