Explorer crashing when searching and naming folders on mapped drives in Win10

Edit: An OS reinstall resolved the below. It's actively finding the space in front of my eyes now. I'll leave it for the reference of anyone else who has problems. Hopefully it also resolved the initial problem.

So I don't know if this is related, but it was brought to my attention that deleting files no longer frees up any space on the NAS. That's a big problem, since it's nearly full and new data needs to be put onto it.

As you can see in the screenshot below, only 18.3TB is 'consumed', but less than 700GB is free on a 21.81TB volume.

I read a bunch of other threads and this KB article on this problem, but we don't have snapshots, and running both balance and defrag only slightly *increased* the disk usage. I haven't scrubbed yet because that takes days, and everything I read suggests that it can't actually fix anything anyway (we use RAID 0).

I logged in via SSH in Putty and tried the commands

# btrfs fi show
# btrfs fi df /data

But they just immediately bring up another blank command prompt, so I'm not sure what I'm doing wrong there.

The files were deleted via Windows Explorer, but they are also absent when I look at the relevant folder in the browser Admin page.

Any thoughts?

I think I'm going to do an OS reinstall, especially since DHCP also started freaking out recently. I really don't want to have to format everything again. I only did that a few months back and it was a huge hassle with this much data.