I don't seem to be having the issues you guys are having running however I am running on asphalt. My shocks are still the same as when I built them two months ago. I run boosted 17.5 on medium to low grip tracks with only a slight variation to the standard Umino setup. Although I prefer the HPI silver springs front and rear. I also fitted the flurine coated shock shafts when I constructed my shocks as per kit with 450 yokomo shock oil. No issues so far touch wood with zero rebound.
Sorry to see you guy's are so disappointed in the car. Shame as it is certainly better than the BD5W which I really liked.
Later,
Calvin