What causes a message to be posted while the attached files haven't finished uploading?

[twofoursixeight]

I think if you click the reply button too quickly (or while the image is loading), it will end up doing this issue. On my end, I can’t click Reply until it is done uploading.

@Canapin

I tried to reproduce the issue by sending a message when my uploads were still uploading, but it won’t send the message until the upload finishes, as expected.

Exactly how I tried to produce it just right now.