Hallo,

Maybe only - bad crystals: change them and try others.

If not - I would do the following for the first:

1. Open the controller box and take a look if all is soldered well (maybe a cable inside the controller is not soldered like it should)

2. Open the tank and take a look if all is soldered well.


Greetings

P.S.:
This will be the start of a great relation to your Tiger I - enjoy it ! [8D]