We had a similar occurrence with a large project file last week (AC10, TeamWork) -- the file went from 50 Mb one day, to 40 Mb the next, and then down to 30-some Mb, with no significant changes made. I just assumed some corrupted element(s) may have been deleted, but I am curious as to what may have caused the file bloat.
MacBook Pro Apple M2 Max, 96 GB of RAM
AC27 US (5003) on Mac OS Ventura 13.6.2
Started on AC4.0 in 91/92/93; full-time user since AC8.1 in 2004