Guided access stuck

Hello i work on a school as it ipad manager.

And one off my students iPad air 2 was stuck on guided access,it said press 3 times homebutton to unlock.

Didnt work and i even used the press 1 time and touch id,but that didn't triggered it also.

Hard reset didnt work neither it went stuck to the guided access,but i managed to find a fix for it.

I focused the device on the Casper Focus,it went off from the guided access(then i did casper off).

Luckily it didnt go back to the guided access,so i went to settings and looked for guided access,it said it was off o.o settings were all default.

Is this a common bug? or how does this trigger while the settings arent even on.

I was just lucky the ipad was on the wifi from the school to fix this,one day i wont be lucky to have it.

Greets

Bert