Clean the engine wheels, clean the pickup rollers and lubricate. Test the Signal strength with this engine. SS is engine dependent. Not just layout and TIU.
When this engine enters this bad section does it loose power? Just loosing signal strength does not cause it to stop, it would just continue moving on the last command. If it stops and lights go out, it has lost power. So either center rail or ground. Testing continuity through wires that pick up track power is also necessary. Broken wire can cause this. Corroded pins inside pickup roller can be issue too even if roller looks good.
By the way, all MTH diesels just have 4 wheels picking up ground. Works fine, just like other manufacturers. G