810s loses signal when docked into DC112a

I know this has been asked before but I can't seem to find the answer.

I have several 810s mobile hot spots. I bought a DC112a to extend the signal & added an external aerial & all was fine for a while then all of a sudden no internet. When I looked at the 810s mobile signal strength & the was just a circle with a bar through it. I found if I took it out of the cradle the signal returned so I connected the aerial to the 810s then to the cradle via the USB & again this worked for a while but then did the same thing. Take it off the Air Card & it worked perfectly (Mostly)

I tried my spares & they all did the same thing. This is all post 2016 & I am sure all devices are the latest firmware. Upon checking 810 build date is Dec 2019 NTG9X40C_11.14.08.40 & I'm sure I updated the 112 too.

I couldn't get it to work so I bought another & without going into it the above happened to the new one.

As soon as any of my 3 or 4 810s are placed in the cradle the 810 loses signal.

Original it was just too boost the signal but I have a few spare old routers they can be configured into wifi extenders but they need to plug into a LAN point to do this.

Has anyone else sorted this out?