Update (and rant):
Contacted CS again ... was asked to send the same screenshots once again, explained the same things once again, got lots of pre-writtten sentences like "i know you feel frustrated, please forgive us", "we understand this is not easy for you, we will do our best to help" but that time, beside being asked to wait some more (my problem was now taged as urgent !) i was told that i would receive an answer by email within 2 days.
Ok i got my email this morning and the answer is "Please change the payment method and try it"
Very helpfull and so wise ;-)
I don't have an other card i could use otherwise i would have tried that without asking, AE's fee on paypal payements is just crazy and i am not willing to register on their own system seeing how they have no clue what's going on with my card.
Well done Aliexpress it looks like you just lost a customer !