Hey Miners, Always check the support forums of the mining pools. Looking at io.pool.mn for example i can see they have experienced problems before with many other coins, so it is not the first time this has happened.
Any pool that operates long enough will have problems with the coins due to the dynamic nature of the coins. The question is how quickly is the pool solving these problems.
I/O wallet update is the culprit in this case - the dev first said that the wallet update is recommended and then suddenly changed the topic to urgent update. Anyways, pool.mn did update the wallet on time and yet the fork happened. What has caused the fork - I have no idea, ask the dev.