You can have a look in the Player.JSON under "Game Options":{ there is an entry: "AI Brake_Grip Usage":0.9725, decreasing this can help in this regard for mods that use this! Not all do - some have theire own settings in .hdv. Another suggestion if AI goes crazy: I noticed that when the rF2 installation is somehow screwed up, it is first noticable in AI-behaviour. Maybe time for a fresh install there?
I have tried reducing AI_Brake_Grip Usage, but the result is the same. [video]https://youtu.be/-dz_1I0Nsfs[/video]
Try more extrem values and look if they go slower (just to confirm that mod uses it). And try "BrakePower Usage" also.
In case the mod's HDV file overrides player.JSON values for "AI Brake_Grip Usage" and "AI Brake_Power Usage", you can also try assigning a setup to the AI: 1) with reduced max pedal force. 2) with brake bias moved forward.
I don't know when blocking became commonplace but it doesn't feel right with the older, low downforce cars. Fortunately it can be turned off. In player.json find AI Logic Override and set it to 1.