haven't heard of that, you can switch your modem back to 11n but a different channel. Move the extender closer to router and test it. Reboot both devices after configuration.

TL-WA850RE V1 doesn't support AP mode. but V2 and V3 can do that

http://www.tp-link.in/download/TL-WR1043ND.html#Utility

oliver44 wrote Try these settings, with settings for your region! The router starts with the date of 2015, delete the old log and make the settings for the region and it will update everything.......

If you still have troubles, it's suggested to call TP-Link support

do you mean wds bridge or ?