One Plus One CM12 update always reboots and starts the "Android is Upgrading..." process

About my Phone: It's a rooted One Plus One with twrp and CM12 installed. I updated CM12 with a Update zip which had to be flashed manually through twrp. When i now want to boot the Phone it always starts "Android is Upgrading...". When the process is finished, the Phone reboots on it's own and runs through the same Process again and again. Does anyone have an idea how stop this and boot normally?