Old thread, but....
After chilling to decant, did you let the yeast slowly warm back up to pitching temps or did you decant right out of the fridge and pitch?
Pitching a cold yeast slurry could be the reason it was a slow starter.
in my experience Ringwood doesn't show crazy fermentation and takes a little longer to run its course.
This is quite the opposite of what this yeast is like. Its a quick fermenter to glass type yeast.