Obviously, the water level was changed because someone decided that it was not correct as it had been.
Unfortunately, changes are sometimes made with little thought to the existing missions that might be broken by the change. Or, the importance of the change outweighs any inconvenience.
Requests for “improvements in realism†in vessel behavior can also break missions that depend upon speeds, stopping distance, or ROT of the player or AI ships.
It is a fact of life that some older missions can be expected to fail as a result of updates. A lot of the CMMs' efforts have been in testing missions to see if they still work for newer versions.
The good news is that there are many missions. There are also many topics on missions that have caused trouble—offering reasons and solutions or corrected versions. One need only look for them.
