Clip usage

Hi all,
Feel free to tell me I'm doing this all wrong, but my typical workflow is:
1. shoot a bunch of stuff and import it into Resolve (17.3.1 Build 5 Studio in Window 10 currently);
2. put together my project (often using multiple timelines for different deliveries);
3. use the media pool 'usage' column to sort and delete all the clips I didn't use (with all timelines open, not that it should make a difference)
4. export the entire project (with media) to archive it.
The problem I'm having is the 'usage' appears to be incredible unreliable. Case-in-point, the attached which shows a clip in-use 7 times but the usage column showing as '0' - several other clips in this project are the same.
I don't want to backup hundreds of extra GBs of video clips I'm not using in the project, and Resolve clearly knows I'm using this clip in the usage menu, but just doesn't update the usage column. I also don't want to have to manually double-check hundreds of clips before I delete them. In the past you could force an update of this column, but that menu item appears to be now gone.
Am I doing something wrong here?? Is there another way to force an update of this column, or otherwise just back-up 'used' media.
I've always been pretty careful working this way in Resolve (never had a single problem with the 'usage' column in Vegas Pro but that's an aside!). It is already weird in the way it marks all timelines as '0' for usage, but this screenshot especially seems to demonstrate just how broken this column actually is right now...
Interested in any thoughts

What specific format(s) are you using? Some are extremely bad for post (particularly Media Management), particularly if the formats don't allow embedding precise timecode on a frame-by-frame basis. H.264, PNG, and TIFFs are offenders here. ProRes, DNxHR, DPX, and EXR can work fine. Certain kinds of H.265 can work OK.

Also, some cheap cameras (particularly cellphone cameras and DSLRs) are sloppy about giving files identical names across multiple cards. When you combine identical conflicting filenames plus no timecode (meaning, 00:00:00:00 on the first frame of every clip), it can add up to a total trainwreck in post. There are workarounds, but you have to set this up from the first day of shooting throughout post.

Thanks for the reply Marc,
Those particular clips are h264 10-bit 4:2:2 from a Sony FX3. There are also a couple of PNGs in the project.
I don't want to be a jerk (or shoot the messenger!) but I'm not sure if that should be an excuse for BMD? None of these are exactly 'obscure' file formats, and Resolve clearly knows the clips are being used (as per the context menu) so just appears that column is broken??
Quite a lot of my projects are quick turn-around (a couple of hours) and I simply don't have time to transcode a morning's worth of footage from perhaps 3 cameras into ProRes (nor do I want to use the extra disk space)...I have to assume I'm not the only one editing in Resolve with native h264 files?
I'd definately be keen to hear about your workaround(s) though. So far, I've landed on adding flags to every bit of footage on all my timelines, then sorting the media pool by 'flags'... It is however, to be clear, a really crappy solution when there already exists a "usage" column in the media pool already.