This is the exact same problem I have found from this thread:
construct.net/en/forum/construct-3/general-discussion-7/3d-camera-plugin-rotation-173217
I'm having this problem too. Setting an intial rotation "on start of layout" may show it right when the layout restarts, but when I move the mouse (camera is set to rotate by mouse movement) the camera jumps back to the previous rotation value and continues from there, not the initial position.
My game on the Scirra arcade exhibits this issue. Die on any level and it will restart facing the level sign, but moving the mouse will snap back to the previous rotation before death. (It's something I keep trying to fix. I worked around it by not having any enemies appear until you are actually in full control of your rotation direction so having to adjust the camera rotation isn't fatal.)
https://www.construct.net/en/free-online-games/vault-peril-32857/play
Maybe someone's come up with a solution in the last few months?