It's not the blocktime.
I've been told the forks were caused by coin-server (which hosts a lot of masternodes) going down.
Apparently every time a significant amout of masternodes go offline at the same time a fork could happen due to the masternode payment enforcement.
This is a serious problem I think.
Sure, people shouldn't use centralized masternode hosting services but realistically, people won't move their masternodes to other more reliable but more expensive hosts.
Something should be done to make sure the network is unaffected if/when a lot of masternodes go offline simultaneously. Otherwise the network can be attacked any time.
I might be wrong though but what's clear that it's a bad timing to have forking issues.