TWRP won't reboot - how to fix it?

After flashing TWRP in fastboot mode I can use it as the default recovery like it should and it works flawlessly except when I want to reboot.
As soon as I click on reboot in TWRP the phone freezes and I have to long press the power button to turn it off.
Is this a known bug or is there a fully working TWRP build somewhere which I can flash in recovery mode (without a PC and fastboot)?
Thanks in advance