Hello there! I suppose you are talking about the Current Time setting.
The issue is due to a change in time calculation that took place in 21.7. You can read more about it in this reply from Cameron under the 21.7 thread. The issue with Current Time being out of sync sometimes is known and is being investigated, as mentioned in the Support FAQ pinned at the top of the category.
Unfortunately, at this time, there is no ETE on when this will be fixed, but rest assured that the team hasn’t forgotten about it and will push a fix once it’s ready.
For now, something you can do in order to maintain the real time is to simply adjust it to whatever the correct time at the country/state you’re flying over is; and check on it every half hour or so. A rather band-aid solution, but it’s really all you can do at the moment. Hope this helps!