Have you tried the 4.1 beta release? The 4.1 (release 3) changelog is extensive and has enough in there that it might solve your issues. I experienced some similar problems when I was traveling a couple of months and ended up compiling my own firmware on a more-stock OpenWRT. I haven’t gotten a chance to test it out yet (will do that in a couple of weeks), but I’ll definitely have the MT1300 on hand as backup.