What causes a "stuck block"
A few elements of answer:


Difficulty readjustment can be done for each block on some altcoins.
Mining is a highly random process, if you keep on flipping a coin all day, you will get long series of faces. Similarly, the miners may get unlucky. Even in bitcoin you see gaps of over an hour.
The above is compounded for altcoins as miners switch from one to another depending on profitability.


So nothing really unusual. As for a fix, bitcoins' testnet uses a rule where difficulty drops to 1 when no block has been found for 20 min. But the security implications should be thought through.