Not going to debate here your decision to stay on 6.2 -- as there is plenty of that in other threads, but as an X-software and technical support kinda guy, the reality likely is as you get further behind in firmware releases, more odd problems may creep up where interfaces to things like the Tesla App (& Remote S or other apps that use the evolving and officially undocumented API) are involved. We know Tesla changed things to introduce Homelink, Summon, etc in both MS firmware, the Tesla App itself, and likely the API. To what degree that involves the door lock logic, or they touched other parts of the API or code that may have broken something interacting with old releases, only Tesla engineers into the bowels of it would perhaps know. I suspect the issue is Tesla does not perform regression testing to ensure everything continues to operate with (much) older firmware releases. Frankly, I wouldn't expect them to, with their standard of pushing new firmware releases out to the fleet, and new Tesla App levels to the App Stores. Sure, customers can continually decline installing a new firmware release in their MS or not updating from the App Store, but that doesn't mean Tesla will or must ensure everything continues to operate with the growing number of code combinations that have ever existed.
All that being said, posting here to find another 6.2 owner was probably a good move. The other thing I'd suggest, is post which App (iPhone or Android) and what release of the Tesla App you are using -- there have been several, and you need to find an owner matching both sides of the equation to really come to a conclusion if it's just you or the specific combination causing issues. Good luck.