I have a LX20 that was running very old firmware. The factory very
helpfully provided me with the firmware upgrade to V5.21.
Installed the firmware and everything appears to be working 100%. Of
course I can't pick up the satelites inside the concrete building I work
in so we will see how it works later.

Ahem - Put LX20 in glider, and get "GPS BAD" on status.

Factory has not responded to my query so the question becomes.
Is this a known problem with older LX20s on new firmware?
Is there something I am doing wrong?
Is there a way to revert to the older firmware to test this? I was on
V3.1 before.