I had the same lack of roll back problems with a pair of Cura 4's last year. No one would reply to my help inquiries through the Formula USA web contact. I finally connected with someone at Formula Italy via the Formula account on Pink Bike. After a couple of back and forth's for help through Pink Bike, Formula stopped responding.
Pretty poor performance from the brakes and even poorer performance from Formula customer service. This is the same combination of problems Formula has been having with their brakes for years.
Reading through the conversations above, it sounds like there may have been some seal issues with the early Cura 4's? I really would have appreciated it if Formula would have stood behind their brakes and helped me out.
YOU LEFT ME HANGING WITH BUNK BRAKES, FORMULA. Weak. I'm now on Saint's.