I have a couple of Samsung tablets on my OneMesh network (an S3 and a Tab A) and although they will connect to the range extender they only get very intermittent data, almost nothing. If they connect to the main router (the AXE75) they work fine! 

I have 40+ other devices that seem to be ok, it's just those that seem to not work via the range extender?

I've tried changing channel bandwidths etc. on the main router but with no improvement.

Has anyone else had issues like this where devices will work on the main router but not the extender?