I had a similar problem with one of my 2025s, although what happened in my case could happen to any engine. It ran for awhile, and then limped to a stop. After a cool down or reversing, it might run again for awhile. It turns out that the engine had been run on track that had been cleaned with steel wool. Believe it or not, it wasn’t that obvious. I used Q-tips to clean every reachable surface and toothpicks to clean out every tooth of every gear. I got marked improvement, but after a day or two the same symptoms returned. I had to repeat the process twice more before all the dregs of the steel wool were finally purged, but after that it performed consistently. That was ten years ago and it still runs well today. I don’t know if this is your problem, but it might be worth a try.