Vince53
Bachmann is a subsidiary of Kader Industries, They posess the molds to Bachmann & the former Aristocraft use to make the B-mann trains. Possibly others too. Elgeebee knockoffs, Riviolli etc.
You might look/see the manufacture date of the trains, if post cv19 pandemic lower employee workforce, quality controll issue.
First, You will want to make sure your power is constant, use a voltage meter to check each piece of track for continuity.
Make sure the track pins and connector slots are clean/ bright for best continuity.
Second,  Now l am not recomending this, but l do it:  On my n-scale trains, if the wheels etc build up crud l take a can of electrical  contact cleaner and spray the wheel assembly down with it until it runs clean. lt works for me.
Make certain you lube well after any cleaning.
I hope this is of some help.
Happy Rails!
dave

Vincw
l just hold them wheels down and spray inside & out & let the contact cleaner do its job.

Vince
Make sure you Lubricate well after cleaning.
my main lubricant is Mobil 1 synthetic oil. a qt is about 7$.
last one l bought should last me practicly forever.

Happy Rails...
dave

Vince
l used to use special bottles with needle type tips sold by various hobby shops.  Now  just get a few syringes from a diabetic friend and load them up. Allows me to put the oil exactly where l want it...
Happy Rails....