Tray developing 4x5: strange marks/scratches

I recently started tray developing 4x5 film (have done 8 sheets so far) and noticed these strange scratches/marks on the film base side of the negs (not on emulsion side). Anyone know what could cause them? They don't look like linear scratches, more like the film base is cracking or peeling. There are smaller marks around the edges of the film, and a few large spots in random places.

These appeared, in various quantities, in all six negatives I processed. You can't see them from the emulsion side so I'm hoping they'll print fine, but would like to avoid them if possible.

Could these be damage caused from scratching along the bottom of the tray? From the film holders pre-development? Something during the drying process? Something else? Below are the materials and process used:

HP5 + (all are from the same box of film)
3 min pre-soak
Dev in Rodinal 1+25 8 min (2 negs at a time in an 8x10 tray, shuffled by lifting one neg out of tray, moving other neg forward to top of tray, and placing removed neg into bottom of tray, once every 30s)
1:4 white vinegar:water stop bath
Ilford Rapid Fixer 1:9 for 5 mins (similar agitation to above)
approx 15 min rinse in a large tray with a Kodak tray siphon, final rinse in a separate tray with Ilfotol
Hung to dry w/alligator clips

Curious as to what this could be. Once again, the emulsion side of the film is flawless - no scratches or marks. These are only appearing on the film base side.
EDIT: photos (can't seem to embed for whatever reason) IMG_3362 | Andrew Korchok | Flickr https://www.flickr.com/photos/33963910@N06/51240108726/

Looks like manufacturer issue. Contact Ilford.

Thanks Andrew - you may be right. I may have to waste a few sheets of film to see if these marks are appearing on unexposed/unhandled film.

Andrew O'Neill said:

Looks like manufacturer issue. Contact Ilford.

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Possibly, but I wouldn't rule out handling damage at this point. Some further inspection is in order before reaching out to the manufacturer.

They look a lot like the corners of other sheets were stabbed into the anti-curl layer on the back during agitation. Or something similar from handling the film while the emulsion was wet. Process a single sheet at a time and see if the issue persists before contacting Ilford. If the sheets are floating loose in the wash tray with the syphon running, that's a really common cause of damage.

I've never seen film receive such damage on the base side during tray development or washing. I'm not saying it isn't possible, just unlikely. One way to find out is to process one sheet in same tray.

Andrew O'Neill said:

I've never seen film receive such damage on the base side during tray development or washing.

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I've only seen something similar on sheet film that was allowed to float freely with several other sheets in a larger tray - and the agitation/ flow pattern of a tray siphon will encourage movement. The edges/ points of sheet film can be quite surprisingly sharp. I've also seen some issues from poor humidity control during pre-processing storage of sheet film.

Some further information: these marks also appear on the edges of the negative, almost as if the top most layer of the film base is chipping off.

I burned a sheet of film just to see if the issue was pre-existing before any exposure/processing. Nothing that I can see, so if it is a manufacturer issue, it’s only evident after the film is processed. Didn’t have time to run through the dev process but that will be my next step. Will do a batch of 2 sheets as before, and a single sheet at a time to compare.

I’m fully expecting this to be user error, but it’s just puzzling. If any of these marks were on the emulsion side, I’d find it much more likely to be from bumping/scratching into each other, but there are absolutely no marks on the emulsion.