help with a failed cpdup assert

[Nikolai Lifanov]

I am trying to sync some pretty similar directories with cpdup over ssh  
and three of them are syncing, but the fourth fails with this:
cpdup: hclink.c:343: hcc_leaf_data: Assertion `trans->windex +  
sizeof(*item) + bytes < 65536' failed.

Additionally it only fails when
source (cpdup slave) <=pull= destination (cpdup master)
and not when
source (cpdup master) =push=> destination (cpdup slave)

What could be causing this?

- Nikolai