We have the same issue. We love to build big castles etc but if we have like thousands of building pieces and you want to demolish one or replace it with another official dlc piece, 99 of 100 times the server crashes.
Ping raises up to 999+

We even tried to build without ANY mods; same issue.

Gportal says that the more pieces are in a certain place, the more the server has to recalculate the whole building, not just the one piece you try to demolish (but they said its a problem on funcoms side)