Most of the slurs in my project disappear every time I open it

It is not the first time that this is happening but now this bug was way more persistent and annoying. It doesn't matter how many times I fix it manually, as soon as I close the file and reopen it the slurs are guaranteed to vanish.
Is there any way to work on musescore 3 without losing the great updates on the score's appearance from musescore 4? The latter is more laggy and always corrupts files, the only reason I keep prefering it is just the better look of the score.