+1 / ditto
This is a major issue that needs a different approach for syncing databases.
(Geek note: I used to be a database programmer and have written extensive syncing code myself. One way out of the dilemma (if coders are lisening here) would be to make Endnote use random UUIDs as (virtually globally) unique record numbers. That way, any record number collisions when syncing and merging databases would be avoided. Just my 2 cents… but the current system is a mess, sorry.)