Okay so if anyone gets this problem.
''Host_EndGame: Map coordinate extents are too large!!''
Here is how you fix it.
Try Alt + p first to look for a problem. If this doesnt work...
Look at your grid if you see anything that is outside of the grid.
Chances are you still cant find anything. You can use map properties too see if anything gets off the grid easely.
If you still cant find it, just think if you used the vertex tool or the carving tool. If you did delete some of the weirdly shaped brushes you made and this should fix it.