This happens because of "How iGP calculates tyres lap".
iGP calculates tyres laps when someone pass the start/finish line, so in some races our pit is before this line, so when we pit iGP "forgets" all the first stint history and print this awful (1) with the current tyre.
This isn't a bug, it's just a "game mechanic"
You could suggest another way to calculate tyre history and write a new thread here
https://igpmanager.com/forum-index/6