I would just tell the maintenance guy what you experienced. Perhaps he already knows what is going on if he has been maintaining the boat
for a while. Also, you can easily check yourself if the rudder
is going all the way over by looking at the tiller arms that turn the rudders.
It's possible the hydraulic steering
has a pressure relief valve that bypasses the steering
cylinder when the rudder reaches the stops. A steering pump
can create high pressure and some systems utilize a pressure relief to prevent stressing the system when novice
helmsman keep trying to turn the rudder too far.
Hynautic systems have a pair of bypass valves. If your boat
uses an older hynautic then perhaps they have come loose and just need to be snugged up.