With "Zink".
This problem appeared during the climb. On the left FMC. Moreover, it remained in any position of the HSI switch. I turned down the brightness on FMC, and when I turned it back on after some time, FMC worked fine.
Without "Zink".
After disabling "Zink", the problem did not occur during the entire flight.
I cannot wait for the DESC VNAV logics fix. Seeing a T/C during the desc phase is frustrating :)... Seeing expected FL such as FL270 just 15 nm before touchdown is frustrating too and so on with other predictions totally broken into the fms.
TY for your attention.