Hello Ossaio,
Great that you share your experience here(even not a good one with the broker).
The EA is not supposed to open any different lots from what you have in the inputs. Especially after 1-week proper trading and then changing the lots, I might guess it is indeed from the broker.
In some brokers, there are these “risk management” people, who are looking at the profitable traders. First they look for people who are trying to play the system, and second, they try to frustrate the profitable traders. I have seen slippage and delay in the orders, but so far have not seen changed values of the orders. That is totally unacceptable. Does this broker have FCA regulation?