Jim, you mentioned in an earlier post that when you set up your programming track. You had no trouble adding your engines and you had a track signal of 10 on that 1 piece of track.
Is there anyway you can come up with at least a 3 ft. Length of track on your layout that you can totally isolate from the rest. A few feet more may even work better. Leave it connected. Just isolated. Whatever channel you used when you programmed the engines. Leave the rest of the layout hooked up to the other channels. Run your wires from that channels output directly to that 3 ft. section. Just use the 2 wires. Nothing else. Sort of like a programming track within your layout.
Your engine should start up as that 1 channel is only feeding that small isolated section. Get it moving and then quickly get it into the test for your track signal. Before it hits the rest of the layout. Even if your signal goes south to say a 1 or 2. The engine will stay at the same speed as long as it sees voltage. Keep watching your track signal. You may even get a few spots that the signal strength isn’t that bad.