I do own the rain sensor but am not using because I have another weather safety device and until the firmware and driver are a bit more solid I'm keeping it off. In the code the default rain check interval is 30 seconds. Because the ASCOM logs (0.5.2.3) reveal that ShutterState is asked for and received once a SECOND!!!! throughout the night I decided to just see how changing raincheck interval impacts that this morning. (After a fine good night!). In the firmware code the notes say clearly that setting rain check interval at 0 turns it off.
So using the ASCOM driver Shutter setup I set it to 0 and then opened the shutter. The result was quite interesting.. The shutter did open but it's speed was probably 1/4th of normal!! After the shutter was open I set the rain check interval back to 30 sec and closed the shutter. The speed was back to normal.
I have said many times in this forum before that given the occasional munging of sent commands that the shutter state logging of once a second is likely the cause of quite a bit of mischief. Now I see that raincheck is as well. Even so my setup runs just fine in all night automation. The ASCOM logs reveal lots of stuff about the firmware.