[Snapshot] Cannot create snapshots

Whenever I try to create a snapshot on my multisite, it does not progress beyond 0% and eventually times out with a 504 error.

Strangely though, if I exclude the media from the snapshot, it initializes immediately and progresses to 100% just fine.

During chat, we went over & through the /uploads directory and removed a bunch of files/folders that may have been interfering, and double-checked system resources & other things in wp-config.php, but all looks good in there.

Can’t figure this one out, can you help please?