I honestly don’t know. As I said this is not an issue I am aware of. If you suspect there is a hardware issue, you can submit a support ticket so we can get the board back to check. But I have a feeling this is a software setup issue. My suggestion is that you wipe out the sd card and install raspbian from scratch. Then install OpenSprinkler firmware and try again. I’ve seen cases where other programs installed on Rpi may cause strange interferences with OpenSprinkler firmware.