Are you on the latest version of Bambu Studio (1.9.4.60)? If not, you may want to update your software. I’m currently running the current version and I attempted to replicate your problem, but I was unable to. Using your example, I started at x=50 and attempted to change to x=51 and it moved to 51 as expected.
If you are on the latest version and you are still experiencing the issue then you’ll need to submit a big report. Not sure how much these kinds of bugs are looked at here, but I’d suggest submitting the bug report on the Bambu Studio GitHub which can be found at Issues · bambulab/BambuStudio · GitHub. Be as detailed as you can with your issue, including software version, OS version, and steps to recreate your problem.