[Elecraft] KAT2 C55 adjustment - jumping 099-000

[ub5_073_oleg]

Folks,

yet another KAT2 SWR bridge null adjustment question.

I can reach 003 mV in ATU CALn mode. But after exiting and
entering CALn again, K2 displays 097, 098, 099, 000, 001 and
so on till it reaches a steady state around 003.

What could it mean? Looks to me like a display value overrun
at 100...

Pin 1 of LM358 has 0V on RX and 3.1V on TUNE.