SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I have a 4 zone system with 4-5 sprinkler heads per zone. Last year 3 of the Rainbird impulse sprinklers on Zone 1 pop up and seems to have enough water pressure but they do not rotate as they should. I replaced all three last year and they seemed to be operating fine all summmer. I winterize all sprinklers last year as ususal. Last week I turned on sprinklers for first time and zone 1 was not working. After I found and repaired a leak on a craked valve manifold for zone all sprinklers heads ( rainbird Maxi paw impulse sprinklers) pop up but the same three that I replaced last year do not rotate. They seem to have enough water pressure since the water streamin from them shoot out about 25 - 30 ft. The other 2 heads on zone 1 rotate just fine. I checked for any leaks and could not find any. All other zone sprinklers work fine. Zone 1 is also the closest zone to valves and water source. I am totally baffled. All three heads I repalced last year can't be all bad. It's strange that the same three are having same problem again. I'm pulling what little hair I have left out totally baffling.