Intermittent Wiper Chatter

my 99 Suburban wipers chatter only in the middle of an intermittent sweep. They work smoothly only low and high.

I've lubed the linkage, and it seems ok. I've read here about the re-soldering on the pulse board, and i did that (as they were indeed cracked) but there is still this one problem.

Is there another trick, or am I looking at a new pulse board?

Got it! I missed one of those soldering spots! Now it works great.

THanks for the advice throughout this forum - the job really was easy, but I wouldn't have tried it without the great help provided here!