Actually the seller told me these springs won't fit all gearboxes. He was quite sure I will have problems with them. So he gave it to me and sold me a BMW OEM one. I decided to give it a try. I was foolish enough not to thoroughly test the gearbox BEFORE putting it back on the machine. So if someone is to blame here, it's me and me alone....
Now the box has made around 200 miles and gear change is going better every day. I think the mechanism has to settle.
As I have to inspect the bike after the 750 miles run in (new rings and valve touch up) I will decide what I do then... But of course your advice is very sound. I can't let the bike like this. I could be dangerous.