Connectivity issue

[Catherine0805]

So I've had Sky Q for years and have 3 minis. One is in the kitchen next door to my living room where my router (Virgin Media) and main box are. 
Another is in my bedroom 2 floors up but never had any issues with connection. Until now. The 3rd is in my sons room but it's not plugged in as he never uses it.  The bedroom one kept losing connection and freezing, lagging and just being a general pain. Done all the usual resets. And restarting router and main box etc... even re-paired it but it just comes up with the MR102 error. 
Sky asked me to switch the minis around so I tried the one that works in the kitchen, upstairs,  and it works perfectly. The other 2, irrelevant of where I put them will not connect and get the MR102 error. 
Sky are sending an engineer out Friday but I'd love to fix it myself. Any ideas? 
Thanks 

[Quoman7]

Hi @Catherine0805 It looks as if you need a SKYQ booster situatated between the main SKYQ box and your Mini boxes, the engineer will provide one if needed.

[Catherine0805]

I don't think i do though because one of them works perfectly and connects even 2 floors away, seemlessly, but the others wont, even if its sat next to the main box/router