Get this in debug.log every block:
GetSpork::Unknown Spork -1866429697
CheckBlock() : skipping transaction locking checks
CheckBlock() : skipping masternode payment checks
Is payment enforcement actually on?
Got the same issue. Can't sync with MN4 or at least it's stuck for like half an hour at one place.
Looking at source and looks like dev typoed the timestamp in the spork.h file. In main.h it's 1428537599(April 8 2015), but in spork.h it's 2428537599(December 16 2046). In checkblock if first checks if time is past the first one and sets a flag true, then checks against the second one, and sets it back false. It then skips the mn payment enforcement code since the flag is false.
So masternode payment enforcement isn't actually on, hardfork is set for 31 years from now.