You’re welcome! Maybe this is be a bug in the recent versions of macOS? I almost didn’t find this tip when I looked for solutions and the Apple support forums don’t mention this fix at all

I recently had a similar problem where system files were filling my entire drive and even grew larger when I deleted files.

The only thing fixing the problem was deleting a faulty local APFS snapshot using disk utility. You can do so by showing APFS snapshots via the menu bar and then checking your system drive. I also had to reboot a couple of times before I could actually delete it.

I Hope this helps!