I'm posting in here as I suspect the issue is the chip. I bought a 37 from ebay and it has various intermittant faults. The lights turn on and off randomly whether selected or not. Its very slow and often randomly stops. I've cleaned the wheels and checked the loco over with no obvious issues.
The Lenz silvers (and golds), have a 'shunting mode' , which restricts the speed , its activated from Function 3, so first job would be to make sure F3 isnt turned on.
After that, the random lights etc would suggest perhaps a loose connection somewhere in the decoder wiring (if its hard wired rather than a socket) , or in th eloco wiring if its a socket installation.
To verify if the chip itself is at fault, the best way would be to reset it to factory defaults, and see if that changes anything in the running.
For Lenz, simply set CV 8 to 33, this sets everything (including the address) back to defaults.
*** I'd certainly combine comments from two previous posts here - if a second hand loco is already chipped, always reset it on day 1 to eliminate anything untoward being adjusted and then do your own CV changes to your own preferences... however Zmil is right, and speed step mismatch is the primary cause of lights doing strange things almost every time. Its rare for internal contact issues to be the issue with lights.
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