Update - problem returned after around 25 hours of additional run time since removing pieces of plastic from the fuel filter. Dealer's service mechanic was at my property today troubleshooting the problem. Drained the fuel tank and ran stiff wire and then air through the fuel lines. Apparently, the positioning of the fuel line from the fuel tank outlet to the fuel filter bowl can cause a problem (slight kink in fuel line). Tight area. Dealer's mechanic moved cab insulation and slightly altered fuel line position from tank to fuel filter. Fuel flow thru the line improved after line was repositioned. Not sure what causes hose to kink, maybe heat related? Only time will tell. Next step, if today's effort doesn't solve the problem, is to remove the fuel tank and replace with a new tank and new fuel lines. Dealer's mechanic said that they have had to replace the fuel tank and fuel lines on two other similar tractors to solve this intermittent stalling problem.
Hope this helps someone else down the road. I will follow-up with updates as additional hours are put on the tractor.