The current behavior of enabling or disabling static NAT will call the apply IP associations method in the management server. The method is not thread-safe. If it's called from multiple threads, each thread will load up the list of public IPs in different states (add or revoke)--correct for the thread, but not correct overall. Depending on execution order on the virtual router, the router can end up with public IPs assigned to it that are not supposed to be on it anymore. When another account acquires the same IP, this of course leads to network problems.
The problem has been in CS since at least 4.2, and likely affects all recently released versions. Affected version is set to 4.7.x because that's what we verified against.