2.5" array speakers stop working

I have 4 F1 Model 812 and  10 F1 Sub speakers.  I LOVE them.  I haven't had any other small PA that comes close to the sound and ease of setup as I do with these.

I just sent two of the 812 cabs back (1 of them for the 2nd time...) to get the 2.5" arrays to work.  When I power them up, the arrays don't work: I need to turn the volume up or down, or smack the side of the cabinet to get them to work.  Does anyone else have this issue?  Is there something I can do to keep from having to send them back?

It is very inconvenient to pack and ship them and be without them for 2-3 weeks and pay $ to get them back for a few months...