Deleting files does not result in freeing up space on internal SSD (not boot volume)

I'm running the latest version of Monterey on a 2017 iMac. I have been running this configuration for many months without issue and earlier today Parallels was complaining about the lack of space. All of my Parallels VMs (4) are located on an internal SSD drive along with my library of videos. I checked and sure enough, Mac reported it only had 34MB left on my 2TB SSD drive! Given Parallels and Videos on that drive, I didn’t doubt that result so I immediately moved a ton of videos off that volume to an external drive, deleted the source files and emptied my trash. I then rebooted, expecting to come up with a bunch of space freed (just one of the folders moved was 140GB) but the system only told me there was 3.4GB free. I started poking around using terminal and l didn't but didn’t find anything--other than I apparently don’t have permissions to run "ls .Trashes" even though I’m an admin and Terminal has full disk access. That’s when I started add things up…I added up the size of the known folders on the drive and found they totalled just under 900GB while the drive size is 2TB! In other words, it seems I should have over 1 TB free on this volume! I finally decided to do a safe boot and look at the free space…and while I was there, I ran First Aid on the internal SSD volume. First Aid ran clean and declared all was well, although I then had just under 30GB free (not sure where the additional space came from). I rebooted to normal mode and yup--30GB free. I used a couple of 3rd party tools to look at volume contents and both verified that I have used <1TB and yet Mac only sees 30GB free on the volume while correctly reporting the volume has 2 TB of total space--it claims I have used 1.97 TB. I booted into recovery mode and ran First Aid on the boot volume and the internal SSD volume. No problems found and on the internal SSD it declared I'm using 1.97TB with only 30GB free. Every tool I know says I'm using less than 900GB of the 2TB SSD. What am I missing?

Most of the fora talk about problems with Macintosh HD (boot volume) and how to address issues with that volume. Few, if any, articles are directed to issues with another internal volume. I can’t help but wonder if I’ve got a permissions problem on that drive that is blocking Mac internal tools from managing the space appropriately. I’m not sure how else to explain this problem. I don't know where to turn next. Any thoughts?