I already heard that F1 2017 has a lot of bugs especially in Multiplayer. But in constrast against the lot of the F1 community, I am patient with the Codies, and try to help them as much as they can, to release a patch as soon as they can ;D
So the following bugs, which are actually the first bugs I have experienced in this game so far, all occurred in the same Online Race. The game mode was Public Matchmaking and in a 5 lap race with One-Shot Quali in Austrlia in the HIstoric Class 1 (Ferrari 2004 to be precise).
The first bug was, that directly at race start, I got the blue flags. I led the field but got constant blue flags, so far that I got a 2 sec time penatly. When the driver in P2 eventually overtook me, the blue flags where gone and when I overtook that same driver again, I still had no blue flags, so the bug solved itself, but still I got a time penalty of of it!
The next bug is probably one that is more common:
At the end of the race, everyone who crossed the line got DSQ'd the moment, we crossed the line.
Adding to that, the game got stuck in loading screen after that!
I hope this helps you in some way and I hope that you can release a patch soon to make this game perfect!