There are at least two issues(three actual in my mind), one is the increased amount of electronics involved with fuel injection, which has become a permanent fact of life for any ski. Eventually the harness connectors WILL corrode on any ski, presence of salt pulls the event forward.
Then, the 951 is a high performance 2 stroke near the edge of design limits, so by design it simply isn't going to last as long as most others. Especially if the scales are somehow tipped unfavorably by a particular event and there are various potential scenarios.
Third, my belief is direct injection simply isn't a friend in the battle of keeping a 2 stroke piston from overheating, which is a common root cause of failure.