John Deere 450H LGP Transmission or Electrical Issue?

Hi all - I currently operate a John Deere 450H LGP dozer. Mainly for forestry site preparation, i.e., furrowing for red pine plantations, scarifying for direct seeding, etc. Furrowing can be rough with lots of bumps and impact to the machine from hitting stumps. This last field season, I was having a reoccurring issue where the dozer would suddenly come to a complete stop, then without operator input, would continue on without ever moving the FNR lever out of F. The first time it occurred, I had just offloaded from the trailer (tilt-bed style) and was tracking into a project site. It hadn't been running for more than 10 minutes. I initially wrote it off, assuming I had the blade too low and had struck a rock. The second time it occurred, I had been furrowing for 4-5 hours and was tracking out at top speed on a flat sand road. No possible obstacles to strike. After this occurrence, I took it into a John Deere dealership where it would not act up for them and no codes had been thrown. Brought it back. The second day of operating and it happened again. This time in reverse after offloading and then again in forward less than 5 minutes later. This time I noticed that when it happened, that all of the lights on the dash lit up accompanied by one long beep. I continued to operate that day and noticed an overall lag in power and response from the dozer when shifting speed and using the decel pedal. Took it back to the dealership and again it wouldn't act up for them and no codes. They changed a fuel filter and discussed the possibility of a bad alternator. Following bringing it back for the second time, I completed ~30 hours of furrowing and never had the issue again. However, there was one occurrence where I had shut the machine off and it wouldn't turn back on fully. Key would turn, panel lit up as normal, then no turnover. This issue was "resolved" by putting the parking brake on and off and pumping the middle brake pedal. This dozer is also used for wildland fire so I am facing a third trip to the dealership to figure it out before fire season. Now a matter of safety rather than an inconvenience. I would appreciate any input from those who have experienced something similar! Let me know if there is more information I can provide. The dozer was built in 2006 and has ~1400 hours on it. I've been running it for 2 years and this past season was the first time it acted up.

Starting point would be checking all battery cable connections, all ground points, unplug inspect and replug all harness connections, any sign of corrosion green is death. Some people like to put a little non-conductive silicone grease in these connectors to hopefully exclude moisture, YMMV. Sounds to me like you may have enough voltage drop somewhere that you're getting a reboot, but I may be all wet too. I love electronics.... when they work.