Modifications to objects occasionally fail with a -659 error.
Time is in sync.
ndstrace with +COLL shows:
2188859136 COLL: [2019/10/09 18:33:54.772] Ignoring request to overwrite future value from entry 0x8092, attr 0x112, vts=2019/10/09 18:33:54, 4, 14 ava->timeStamp=2019/10/09 18:33:54, 2, 41, returning failed, time not synchronized (-659).
Notice the updates got replicated in the same second causing the modification to collide and result in the -659 error
Synchronization in eDir 9.1.X is substantially faster by default that earlier versions increasing the possibility of modifications synchronizing very quickly and possibly occurring in the same second.
Setting the environment variable NDSD_CC_SKULK_DELAY=2, creates a slight delay and prevents the possibility of the modification collision in synchronization.