My browser / operating system: Windows NT 10.0, Chrome 89.0.4389.114, No Flash version detected
So, I was making a “Aesthetic username generator” And I had about 15 costumes for each sprite. When I was done, everything looked fine. Then, I saved it, and everything was still fine. I pressed “see project page” and I saw that about 1/3 of my costumes had turned into grey boxes with a black question mark, the question mark was in the “Helvetica” font. Some of the question marks were out of the box too. I pressed “see inside” and fixed them (By redrawing them) and pressed “see project page.” after doing this about 3 times they seem to work, but this glitch is annoying. They only turned into grey boxes after saving, pressing “see project page” and reloading. This is the most detailed response I can give, if you have any questions feel free to ask!

Happens to me too IDK how to fix it

OMG i just made the EXACT same topic! omg im so mad at scratch rn! ughhhhhh! they were there before, and then as I'm watching my project they get replaced by question mark, and I'm like what the? And they're even like that in the costumes list!

Yeah EXACT same for me omg its soooooo annoying!

UPDATE-
So, In the “costumes” tab, it is a grey box, with a sans-serif, black question mark, to the top left, but in the project screen it is a grey box with a serif question mark in the middle of the box, that is weird.

This happened to me too, and I seen other people who are sharing projects about this weird glitch. Its going all around scratch!

UPDATE-
You don't have to share the project for it to turn into questions marks, one of my unshared projects had this glitch too.

The sprites got corrupted, you can't get them back without a redraw/reupload.

My costumes turn into question marks too

SxnnyViibes- wrote:

My browser / operating system: Windows NT 10.0, Chrome 89.0.4389.114, No Flash version detected
So, I was making a “Aesthetic username generator” And I had about 15 costumes for each sprite. When I was done, everything looked fine. Then, I saved it, and everything was still fine. I pressed “see project page” and I saw that about 1/3 of my costumes had turned into grey boxes with a black question mark, the question mark was in the “Helvetica” font. Some of the question marks were out of the box too. I pressed “see inside” and fixed them (By redrawing them) and pressed “see project page.” after doing this about 3 times they seem to work, but this glitch is annoying. They only turned into grey boxes after saving, pressing “see project page” and reloading. This is the most detailed response I can give, if you have any questions feel free to ask!

Those question marks are supposed to be placeholders that appear when a costume is corrupted by something for various reasons.
Normally if this happens, its suggested to simply reload the page and to NOT go into the code editor or save it with the question marks still around.

(Side note: OOPS, i didnt look at the dates. Oh well. I'll just report this thread to be closed to avoid this again, sorry!)