From what I can understand from the OP's post above, he wasn't aware or did not know that deposits taking bonuses have a capped max win withdrawal restricton - this is a standard term at almost all casinos.
Next, the OP also doesn't realise that the 2181 EUR capped amount need to be WITHDRAWN FIRST before any new winnings (won with a new deposit) can be considered! He carried on playing, boosted his winniings to 9000 EUR, but is STILL LIMITED to that same 2181 EUR capped allowable withdraw amount - this is also yet one more standard term but is not usually indicated in the casino's T&C! I don't know if this term is indicated at SpinAura or not.
Looks to me that the casino hasn't done anything wrong, but I don't know the real whole story!