thanks for the input, it was a loose connection on the card

Possibly something wrong with the 1A contactor like the contact tips not making a good connection???

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.

The reason I ruled out the rectifier, there are no codes...and he doesn't have to re-key the truck. That points me to the traction pot. With a fleet of 30 RC3000's , with most over 20,000 hrs, I've only replaced (1) 1rec.....countless 4 recs, and about 15 pots with this same condition. Of course, assuming all the switches test good.

Ifixit,
actually i've seen many #1 Rec's and 2 and 5's as well test good with a meter, or even a handyman tester in normal mode and still be faulty. Truck would run but still fault out intermittently because of an internal fault inside the Rec. The handyman tester has a 'leak test' mode where you can check for bleed back through the rec and this usually tells the tale. When you run the test if it turns on the leak light of course replace the rec, even if just blips for a second thats an indication the rec has issues. So the notion that it either works or not 'on or off' is a misnomer (misconception). Just a couple milivolts of feedback can cause one to fault and may not show up under normal testing.
In a perfect world or from a trainer's view though you are correct, most of the time it's either on or off, working or broken ;o).

The 1 rec either works, or it doesn't. Same with the 2 and 5 rec turning it on and off.

Even though the traction pot shows good resistance down to zero(full speed input), the pot is actually bad. The traction card will still see milli-ohms out of that pot.

Since you do not have to rekey to travel again the GE EV-100 card is not faulting out so the problem must be what the card is not seeing causing the truck to cut out. Check your inputs to the card at the 6 screw terminals to see what you are loosing at half throttle compared to full throttle. If none of them fail then check the two bolt terminals at the 1 Rec to see if they fail.