There’s like a 1/10 chance of it happening, as I have experienced it quite a few times as I upload many many things regularly.
When uploading a decal or audio, there is a chance that when it has finished sending the data to the servers, the upload and browse button turns into the top bar and I have no idea why and how to repro it exactly 100% of the time. When it has finished loading the data, it doesn’t actually upload it or take your robux.
In chrome you can see the “Uploading X%…” in the bottom left, and then it says “Waiting for ROBLOX” or something then the upload area is replaced with that after that notification dissapears.