For sure we're all crazy, but this is real!
Yeah this has been happenning for weeks now, but you would notice inmediately after uploading, as you say, deleting and uploading again fixed it.
Aware of this issue, I always check the attachments after uploading.
That post was ok, but then a picture uploaded to a different thread got there.
So that's a more serious issue. You could be breaking you -perhabs- hard work by uploading pictures to new posts.
Two months later someones replies about a picture that went wrong, asking for reupload, but you don't have it anymore!
Your work went straight to waste!