I also posted a comment about how to fix this, but if you cant find it, I made this discussion version too.

An easy fix for this is to download a map from the workshop that says it has a "navmesh". If you are actually tech literate, go to your console (If you don't know how, search it up on the guides) and enter the "nav_generate" command, This will make your game freeze and reload the map. If you use the "nav_generate" command and it doesn't do anything, try unpausing the game. Once you are done using the "nav_generate" command, you should enter "nav_save" to save the "navmesh" it created for your Gargitron.