ifixit,
of course, and knowing the crown design and GE EV100 design i agree, it probably isn't the 1Rec causing the 1A contactor to drop out. (i was just stating my view on what you had said earlier).

As you say it may be the pot just not getting to the range the logic is looking for to allow the card to reach the 80% or above pulse rate it wants to see before telling the 1A to pull in. It could also be some internal setting in the logic card itself causing a PMT or 1A timing issue or some 1A thermal problem causing it to drop in and out as he described.
Replacing the pot would be easy enough for starters providing it checks out to be faulty.
The fact that it only cuts out after 1A pulls in and returns back to normal SCR operation (without cycling the key) leads me to believe it may be something else but checking the pot would probably be one of the first things i would do before going on to other possible causes.
If he were to check it and find a glitch then yes a pot doesn't cost much and as i said is easy enough to replace and setup.
Things he should probably check for:
-If the pot shaft has slipped and gotten out of adjustment
-when testing doesn't read the expected 4300 to 4600 ohms and 5000 ohms when within 2deg of neutral position, and 0 to 200 ohms when in full fwd/rev or shows erratic changes during the sweep of it's internal wiper.
-And yes, there are those peksy switches to rule out too ;o)

Now being this unit probably has an LX logic in it there are no 1A switches on the control handle controlling the 1A circuit so we can rule out that possibility. Verifying the readings on the pot sweep will tell the tale.