I think I have found a bug in the UDP data stream. I am using a Node.JS UDP parser with F1 25 support (https://www.npmjs.com/package/@deltazeroproduction/f1-udp-parser) and while it's working fine, I think I have run into a game bug.
As I am using it for creating custom overlays, I am trying to use data from UDP stream, and I seem to have run into an issue - when I'm loading into a new session of Time Trial and there is a Personal Best time already set for that track, it seems that the game reports the "bestSectorXLapNum" (replace X with sector numbers) and "bestLapNum" fields in Session History packet as "199" for the player car ID. Even after setting a few "legal" laps, values do not update and stay at "199", which should be impossible as the amount of laps saved in the Session History is maxed out at 100. The value is "199" as well without even setting one lap in the session! So I think it is likely a game bug - the parser gives me correct information for tracks with no initial personal best time set (values are at "0" when loaded into the session) and in all other session types as well. I hope it should be a simple enough bug to fix.
For reference, this is the example of what I'm getting in browser's console output when I load into a track in Time Trial with PB already set:
Stored session history for car index 0:
Object { numLaps: 1, bestLapNum: 199, bestSector1LapNum: 199, bestSector2LapNum: 199, bestSector3LapNum: 199, lapHistory: (100) […] }
I do realize that using Time Trial packet could be viable alternative, but I think it could be worth to check and fix the output here as well.