>>/19766/
Wow, didn't expect you to really answer, appreciate it man.

I use app called Dashchan on Android. This is like imageboard browser. Few days before I made this thread everything was fine, I used this app for endchan for at least a year or two, it was working good, and than suddenly error happend.
Btw there was no update for app in this period, so I think it has nothing to do with it (and other imagebords works fine here).

And there is fork of this app and I met anon who said thar this fork has the same problem with endchan.

I dont know if this will help, but when I post from dashchan in bords where you can see user agent in your post mine show mobile safari when I post in dashchan