New clients trying to sync calculate retarget using KGW from block 1120000 and onwards, but krugercoin.miners-pool.eu has already calculated that block and added it to their chain using the old algo. So the local client will say hang on, the difficulty retarget that krugercoin.miners-pool.eu is suggesting is not the same as mine; disconnect for misbehaving.
You're right! The block 1120000 is on old algo, even miners-pool blockchain is broken! (1120000 was definitely not a good setting)
I shut down pool on miners-pool.eu, blockchain is broken, we have to wait a new version with checkpoints.
I don't think you need to shut down your pool, so long as everyone (or at least the dev) accepts the miners-pool.eu blockchain as the de facto official chain.
There is a workaround I can think of:
1. Use the old client to sync, which should get to block 1121075 (when miners-pool.eu upgraded). If you're lucky it will stall here... if unlucky, it will pick up another chain.
2. Change to new client and it should sync completely.
Releasing a new version of the client that only activates KGW past block 1121075 should achieve the same thing.
This needs to be done ASAP.