Problem with Duplo battery train

[Dav1d]

A friend has asked if I could get an old Duplo train working.

It is the train from set 2741 or 2745.

I managed eventually to remove the battery cover and put in new Duracell AA batteries but nothing happens when I press the red button

on the top.

It is in good condition - the contacts are not corroded. It looks very difficult to open it up and look at the actual motor.

Does anyone have any advice on what could be the problem?

Thanks

[Dutchiedoughnut]

Do you have any way to measure voltage at the electrical contacts?