Having lost heaps of things I have written into the text entry field, I have gotten into the habit of doing a CTRL-A and CTRL-C of the whole text field once I get past a few lines of text. That way I can just paste it back into the text field if I have a glitch. If it's something I really value I will paste the text into a text file for safety. Trying to post something yesterday I had a number of .php errors and the way I worked around it was to close the browser and try again. Navigating back and forth didn't fix anything. Seems to have been happening more in the last few days than normal.
Even after that I still couldn't attach an image. I found I could make a fresh post with just an image, then go back and edit it to add text and that seemed to work.
It's clunky but at least it is a way to post if encountering issues. Having worked in an AV post production environment, its easier to accept as a way of working. Everything should be backed up every few minutes in such an environment so I'm pre-conditioned for it, others may not be so accepting.
I'm using Firefox on Mac.