If you follow these rules it works 99% of the time.
- Before posting an attachment, leave the page and come back (go to the prior page in the thread and then push LAST, or close the thread and reopen the last page, or etc). The page must be freshly loaded. My theory is this gets the javascript into a clean state. If you've made so much as 1 post, the next post will not load&keep an attachment. It may look like it loaded, but it'll disappear.
- After adding a post with an attachment, leave the page and come back. GOC automatically gets rid of orphaned attachments every 2 minutes, and the quickest way to convince GOC that its not an orphaned attachment is to get it to display a fresh page with that attachment on it. Failure to do this step and you may discover fifteen minutes latter than an attachment that clearly uploaded, is gone (auto deleted).
This means for every post with an attachment you add to a thread, you have to push four buttons (previous, last) then add your post and then push (previous, last) again.
It's been my experience with the Laugh thread, that if you do these steps, your attachments will hold.
When adding an attachment by pushing INSERT IMAGE, if it asks for a URL rather than a From Computer file upload, this is a HINT the javascript is in a bad state. If this is the second/third attachment in the same post, then it's usually okay to continue. But if this is the first attachment in a new post, abandon the post and go to step 1.