Bachmann old 37 with movement but no sound

[PaulRhB]

I’ve had this a few years and it’s suddenly started acting strangely. 
 

 

It runs fine but if you try to turn on sound on F1 while at a stand it doesn’t go and makes no noise at all. No broken wires that I can see and I tried resetting the chip too.
Turn on F1 while moving and again no sound but it doesn’t affect the running. It seems to be pressing F1 while stationary that locks it until there’s a direction change command. 

You have to turn it off and reverse direction and then it runs fine again. If you are running and use the stop button it will restart even with F1 on. A couple of times it went the same direction even when direction changed. Lift one side off the track and it behaves again.

 
I reset it and it runs fine but still no sound and again if you turn on F1 and then start it just sits there. No other functions are on and none do anything sound wise. 

I’m wondering if this is a sign of the amp dying but why does it stop it from moving under one condition but not if stopped with the stop button? Very odd, the other two run fine on the same Piko controller so it’s not that causing the issue. 
Any ideas?