PPPoE client issues

We recently installed a campus type site with 20 end users all accessing as PPPoE clients, in the main it works well but now and again some users can’t connect until we reboot the switch they are connect through. The end users that are affected are using a sonicwall and a tplink unit

is anyone else having an issue like this and where would I even start looking


attached is a topology of the site
Topology.jpg