Too much timing???

Roger. FWIW..... It all depends on the rising versus falling edge characteristics of the output AND the surrounding circuits. Photocells will tend to always turn on very quickly and sharply. The turn-off can be lazy and unpredictable, or it can be sharp; that depends on the loading that the circuit that is being driven presents to the photocell. If it is a heavy load, then it will quickly drain the residual charge out of the middle ('intrinsic') portion of the photocell semiconductor junction and the turn-off will be quick and sharp. If lightly loaded, the turn-off will be lazy. So if you somehow reversed the leads and could trigger off of a lazy photocell turn-off edge, it would be unpredictable......just like the Mopar's Hall effect sensor. As said...FWIW.. just a possibility for the OP's timing changes with hot temps.