Metadata on two images (MP4) is locked for editing in CO Windows

I use PhotoMechanic Plus. Up to now I haven't used a catalog. I rename the files upon import/ingest, and apply metadata and GPS coordinates. There are a few fields that I have not used before, but am now for images taken for certain events, e.g. job ID. I was having trouble getting my selection of images to match using a filter in CO, in which I'm still using sessions. I figured out or worked around some of it, and had to change a few things so in some cases applying blank metadata to a field to delete it, or just deleting it like if I decided not to include that one after all so deleted the job number.

It's more difficult because the images are in two different folders (I keep my phone images separate). I wish I could select more than one, or more than one date filter. I don't see a way to include subfolders like in Lightroom, either.

I've gotten the count difference down, but there is still a difference between the PM count and the CO count. Part of it is, for some reason at some point, two MP4 files have stopped accepting the metadata changes I do in PM (but later it worked again) .The other files are ok, any type.

Some of it is there, but they still have the job ID no matter what I do. Normally changes done in PM appear quickly in CO. The XMP file looks ok, but I cannot edit any of the metadata in the metadata tab. It's like the inability to even manually enter GPS coordinates, it turns orange but does not change to input, so I can't delete the job number. I can change the color tag and the star rating in the preview thumbnail, but nothing in the Metadata tab.

I checked the Windows file security and it was the same as other files. I tried renaming the XMP file, then PM rewrote it after a couple of minutes. I tried editing the XMP just to see if that would work. I tried sending the images to trash (I thought they didn't actually get deleted but I may have changed a setting some time ago if there is one). Anyway, I dragged them back to the Explorer folder they were in. 

There must be a better way to keep these in "sync" as far as the selection. I found where to exclude the extra variants. 

Any ideas on the non-editable metadata?

And if anyone has a better way of working with PM and CO let me know your workflow. PM's support is good, CO has not been.

TIA