Sorry late getting back to you @R_Rabbit10Antenna's and antenna connectors are intact and clean. Batteries are at 90-96% health, age varies from a few years to a few months, but they do get swabbed out for fully charged ones if needed.
EX K 4.51.02 for the NX5400 and K 4.30.00 for the NX5200. These are the latest ones I received from our dealer. They tell me there are no newer firmware version available for the radios to be compatible with the Harris system they connect to.
5.20 addressed some new Harris things.
Did your dealer send 5.20 to you to test? (yes, you can rollback FW on KWD's)
All points mentioned are very true and valid, bench testing the radio the first step to ironing out
the issue.
SECOND is to contact Tech Support. Talk to Javier or Clanney, if you can get him.
(tech support info can be obtained from the sticky post on LMC2.01 info)
**
Kenwood LMR Tech Support
Support portal @ https://lmrsupport.kenwood.com
(800)752-0987
**