The ETAs for waypoints are calculated in a false manner, and are in the past. only when opening the TIME-Page in the POSITION tab they are updated.
After leaving the page the ETAs gradually work their way down into the past and become wrong again.

the first screenshot shows an ETA in the past (compared to the current time)

The second screenshot shows updated and correct times after opening the TIME-Page

MSFS2020
A350 v1.1.6

nothing particular to recreate the behaviour, just occurs every flight.
in this case from KLAS to LSZH

tested WX ON/OFF on the EFIS, different PERM DATA SETUP modes, but to no avail

noticed it in the version before, but thought it would be a one off.

For me what helps is the FMS2 to set on display TIME panel. Then it works normally. 

Hello,

Apologies for the delay. We're aware of the problem and are hopeful to introduce a fix in the coming update. 

Thank you for your patience. 🙂