I am having a terrible problem with the wifi and APN on my Galaxy Tab A SM-T355Y.
I am with Telstra as my provider, since having the tablet there have been 3 APNs stored by default, two of which are locked.
I run at Netgear CG3100D modem router in bridge mode with a Asus AC3200 tri-band router.
The phone constantly has disconnect issues associated with Telstra.wap. I find it to be stable when I switch to Telstra.internet, however no matter what I do, the tablet always defaults back to the locked Telstra.wap APN and then I get instability again. It would usually take a couple minutes to default back to the locked APN.
If possible I would like to be able to delete the Telstra.wap APN so the tablet will always stay on the Telstra.internet. It's very frustrating as I use this everyday. I'm not sure why but this only happens at home, and I've tried every other solution I could possibly find, the most stable I've gotten it at now is having the tablet assigned a static IP from my router. The problem is still pretty bad though.
I am running TWRP and SuperSU on the tablet, and I've tried the APN backup & restore app, it doesn't work on Marshmallow though.
Any assistance if possible would be great, thanks.