Maybe an approach for you:
Install the alternative firmware (‘SIP’) if you have the Opensprinkler board on top of a normal Raspberry.
,,This is an updated version of the Python Interval Program for OpenSprinkler”
Working flawless since 5 years here and has IMHO much more flexibility as the unified firmware.
In this firmware You can add my plugin (see seperate topic with the updates) and everything works again with wunderground.