TobyMac

They could both be Pearl Gold. This color is known to have some different shades

Looks like a bug. @NathanNathanmaybe something going wrong with an add?

Which set is it? It could be that there are multiple inventory versions of the set. If you for instance have V1 added to your set list, and the calculation looks at V2.

You also have a couple of sets marked as Build. THe part might be in there

What is the total count of 15391 that's needed? Maybe it's 1 more than you totally have, leaving this 1 open? And do you have all set and part lists activated for use in the calculation?

Can you compare with the inventory of 75090-2? There are 2 versions of this set known.

There is the option to export an inventory with or without spares into a Rebrickable csv. You can then import it into a part list. But it won't look at lost parts though

There are some known bugs in the 'Build set' function. Sometimes you even get a negative build count. @Nathan Do you have more info on this?

Before we approve a (Premium) MOC, we always download a copy to make sure the instructions are correct. After that, we delete the copy.

Depending on the brick, both. I have added all standard bricks to the database.

Last night (or for him: this morning) Nathan has implemented a new system for thumbnails. The yellow 3021 has reappeared. If you find any other errors, please let us know.

Because it's only listed in spares in red

I've thrown it over to the admin forum to come up with a uniform solution

I'll gladly reverse the policy ? I'm not sure why we changed it, I think because of the change to add stickers to the main inventory, this went over as well? EDIT: It might also have to do with sets that like the 3in1 that don't have a main model. Those often have parts that are all used in every model, so we chose for the instruction list.

That's been changing lately. It used to be every part that is in the box, but not used in the instructions. Like for example your case with the 21302-1. This is now changed to: Every part that is listed in the back of the instructions + sticker sheet. Seen the instructions for the 21302-1 lists all cutlery, all those parts are in the inventory.