I don’t have a solution for Dashingdon specifically - with that said, it has been my experience that most betas had specific dates for releases of new material laid out.
Assuming this is the case here, the beta testers should be asked to close any copy currently being played and reload from the link on those specific dates. It is on that point going forward I’d expect feedback on the new material being accepted. Anything prior, I’d not use for the possibilities of user error experienced from such glitches.
Also - make sure your testers realize that they should be opening a new copy of the game in a new private window (or equivalent) each and every testing session they preform. “Refreshing” the game within the old window does not work because the browsers (in my experience) still often have residual cache issues.
Unless @dashingdon can cause a system disconnect whenever the author does updates to occur, I don’t see any solution other then changing the link every update - which is fine for major updates but can be PITA for minor things.