I'm seeing something similar after installing Firefox on my phone.
If I reply to virtually any thread, when I hit "post reply" the page hangs. Often times it will post incomplete posts/stale information.
I had to edit a post two or three times the other day because there was a random typo at the end of a sentence but the corrections wouldn't "take".
Is there a save-your-draft-as-you-type feature? I have a hunch it is broken on Firefox mobile