[Elecraft] K3 - Display flashes "thr 4 OFF" intermittently

[Dave Fugleberg]

I've noticed some strange behavior with my K3 lately.  Sometimes the
display will flash twice very quickly and beep twice. I had to take a video
with my phone to see what it says because it happens quickly.  The upper
part of the LCD says "thr    4", and the lower part says "OFF" when this
happens.
This seems to be triggered when I do one of these three things:
Change band with the BAND button
Change band via CAT command
Press, then release the REV button.

It doesn't seem to hurt anything, but it's sure annoying.

The only thing i can find in the menus remotely close to this is the AGC
Onset point, (which IS set to 4 on my rig), but that display in the menu
shows 004 on top and AGC THR on the bottom.

Any ideas what causes this? The radio SN is in the low 8000s.

73 de W0ZF