Code 55, Where Are You?

[faraway]

I had similar symptoms on my layout after the last rebuild. It was caused by dirt on rails (a couple of consistent spots) and wheels (randomly around the layout). The tricky part was the kind of dirt. It was a lot of very robust but hard to see/find white glue etc. on wheels and tracks. I had to use the normally not recommended cleaning blocks to get the tracks back in line and run the engines on alcohol soaked fabric for quite a while.

Your concern about Microengineering code 55 flex being in general the cause looks very unlikely to me. The internet would be full with warnings and bad experience reports about a none reliable track system.

Good luck!