I don't want to step into providing tech suppport for Rain Bird here so I will tread lightly. One suggestion would be to swap this face pack with a fresh one and see if the problem follows the face pack.......or not. If the same exact thing happens to a "new" face pack that previously had been tested and working properly at another site, then you start looking at the cabinet/power supply components or the actual voltage and power supply at the problem site.
This isn't the best answer (above), but you see where I'm going. New Face Pack "Y" works correctly. Original Face Pack "X" has the same problem when moved to another site. And so on. These mystery problems are best solved when you run a comparison test, but that's time and money. Check with Rain Bird to see what they have seen. If you have dirty power at the site, strange things can and will happen. Good luck.