In my experience there was always a character limit for descriptions of around 900/1000 characters - maybe the limit was recently raised on publish but is still getting randomly applied afterwards for some reason?
Yes, this happens to me all the time. I can enter a description fine, and it appears fine online. Then it seems that something on the Roblox end truncates the description. It is hard to track down exactly what is causing the problem since it happens randomly.
One theory I had was that updating a game via Roblox Studio sometimes causes the description to be truncated for some reason.
This also happened on a test place where I entered 4000 characters into the description just fine, but it got cut down to 991 characters at a later time (the original character limit that’s always been in place for descriptions).
To clarify, Roblox used to never let you enter a description longer than that in the first place. It’s only some recent undocumented change that allowed you to enter longer descriptions, but they’re still getting cut down to the original limit later on.
The solution for now is simply to shorten your description to be below 991 characters, and hopefully Roblox can fix it so this 991 character limit doesn’t get applied anymore (whether the limit changes are intentional or not, they really need to be raised, 991 characters is annoyingly short for all the important info we may want in the description)