Can't tether since updating to Marshmallow...

As the title says.

I recently updated my phone (Z3 Compact D5803) to Marshmallow (6.0.1) and since then I've been unable to tether. I constantly get "Error occurred during tethering" and if I do connect a device to my phone, said device does not have internet access.

I've done this: http://www.lukecjdavis.com/fix-internet-tethering-on-lollipop-xperia-z3-plus-other-android-devices/
and this works for about a day but I always have to do it again.

Does anyone know a way I can fix tethering on my phone? I'm on Three if that matters, but I don't think it does because my sim can tether in other phones, just not my Z3C...


Thanks.