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