Reboot instead of shutdown with Veyon "power down" button.

[cvalda]

When I power down a PC via the veyon "power down" button, some computers immediately restart instead of shutting down. This only happens when using Veyon, other ways to power down work fine.
The computers are the same build and OS is distributed centrally over network, there should be no remarkable differences between them.
I'm interested in knowing exactly what signal does Veyon send with the "power down" button and what could be the cause of this behaviour.