hard drive space disappears then returns after restart

[flat6pilot]

2020 iMac 27 running Sequoia 15.2. 64GB.

My iMac has about 80 GB free on the drive. Once I log into the computer, the amount of free space slowly starts decreasing to zero after a few days. All I have to do is restart the computer, and suddenly I have 80 GB free again and the cycle starts all over.

This started a few weeks ago, have not installed new software or visited suspicious websites.

I checked the memory tab in activity monitor and don't see any applications using 80GB. Brave is usually the highest using around 2GB.

Any ideas?

 

[gilby101]

DaisyDisk https://daisydiskapp.com/ to see what is using your disk space. Make sure you scan as administrator.

 

[HobeSoundDarryl]

When it gets to zero, can you still write to the drive? In other words, is this a space reporting bug or something is actually- but apparently only temporarily- eating up the HDD space? Why don't you work it down to 0GB and then see if you can copy a big file onto it? If so, does it still show 0GB or perhaps negative GBs?

Have you used Disk Utility to run First Aid on the drive?

 

[Bigwaff]

Turn off Time Machine backups. Does problem still happen?