If it happens on particular switches, you have to locate the offending spots. Time consuming. You have to watch the engine as it passes over the switch. You'll see the wheels (usually in the trucks) rattling back and forth. Look for sparks. Then start with large pieces of tape. If it stops stalling, reduce the size of the tape strip until you've covered the spot with a small piece. You can even push/pull the engine over the switch. If it's only happening over switches, this may be your issue. I hope so......cheap fix.
Another thing to consider (also easy fix) is a loose e-unit attachment screw or......a loose lever. If the lever is loose, I jam a thin piece of styrene behind it to tighten it (creates much better contact).
