Hello, Chris
I examined the documentation before I posted the initial question. The problem is that documentation is not clear at all on this issue.
Basically, I can derive from it 2 mutually exclusive conclusions:
1. If this warning comes without any error - ignore it altogether, because there was no actual failure
2. There was an real failure and rows were not synchronized, but we just cannot tell you why.
Obviously, both cannot be true.
So, I need a clarification on this - was there an actual problem, or wasn't there? Were rows synchronized or not, or, may be, the synchronization command (for example DELETE) arrived when there were no rows to delete.