Google says title changes don’t impact rankings

“This just changes the displayed titles, it doesn’t change ranking or takes [sic] anything different into account,” he elaborated.

Why we care

This means the titles you wrote may still be taken into account by Google when it ranks results. So, don’t stop optimizing your titles just because they may change in the search results. If your clickthrough rates have taken a hit, you can use a third-party tool to check whether Google changed your titles and if it did, it may be worthwhile to experiment with a new title. If, on the other hand, your clickthrough rates have improved, you might want to make note of how Google changed your title for future reference.

That having been said, Google makes ranking changes very often, so you may experience rankings fluctuations, but they won’t be due to title changes.