I imagine you may not have had a valid warranty and so bought the bottom module independent of Fairphone’s ‘instructions’ however the module is guaranteed for two years, so you could contact Fairphone to see what they say.
Regarding the issue. As you had tried alternative cables and chargers I can see why you bought the new bottom module.
However:
That it charged from a power bank may mean the plug and socket were a better physical match.
Despite all the alternatives you tried there is no indication, here, that any match of cable and charger were suitable despite the facts that a) they may have worked and b) may work elsewhere.
I am inclined to think than if the USB port is clean then the contacts on the core module may not be.
It would be worth removing them module and cleaning the contacts that you can access.
You could also dismantle the old bottom module and clean that more thoroughly.
Please check that the water maker is not red too etc.