Nextbot navmesh -black mesh- causing massive lag

So I am working on generating a Navmesh for a map, however I am running into a problem. If a player sits in a prop that is raised off the ground the bots will attempt to phase through them and cause horrendous FPS drop down to about 1 FPS. I have tried splicing, marking as jumpable area, generally everything I know about navmeshes, but it still isn’t working.

Picture of the black mesh:

Picture of prop:

All ideas are appreciated.

The best I can think of is developing some ways for the nextbot to realize the player is on the prop, and what to do when they are.
You could use traces for this, and range checking. The drop in fps thing is sort of strange, never experienced that really when working with nextbots.
Are you using a public nextbot or one you made yourself? If it’s public or yours, would you mind showing a bit of code?

I’ve been told that if a nextbot targets a player that can’t be reached via the navmesh it will lag horribly. Try making the nextbot stop targeting the player if they can’t be reached and see if that fixes the lag.