This started a few days ago.

I'm writing a post and add an attachment which shows as a thumbnail onscreen. I double-click to edit the attachment and everything greys out (see below). I can't choose to change size or alignment. I end up closing the tab and starting again with the post, and the same thing happens, so eventually I make the post without the attachment (or so I believe).

Click image for larger version (This was added using 'Manage Attachments' and I have not tried to edit it just in case .)

But then when I view the post, the attachment is there. I don't see it on screen anywhere while I'm posting, but it seems to be still attached in some way.

Here is a thread where I've ended up with 2 attachments in one post, and one attachment in an earlier post of the thread (where I had commented about being unable to attach, then it appeared anyway):

Laptop freezes and have to power down

In the post with the 2 identical attachments I added the attachment by using 'Manage Attachments'. It had uploaded from my earlier attempt and was lurking somewhere when I started the new post. But then when I viewed the post the original attachment was sitting there as well, at the bottom of the post.

So I try to edit the post to remove the erroneous attachment but I can't.

What am I doing wrong?