UBB.threads PHP Forum Software Community Forums UBB.threads 6 Version 6 Bug Reports Private message, no Subject: Text is erased

I am running Threads 7.1, got a gripe from a user here.

If you compose a private message and then submit without a subject line, the nag screen comes back telling you to use the back button. But when you do, all the text in the post is wiped out.