When I start off with a brand new map, I seem to be getting residual changes from my previous ones.
I don’t know if it’s from my custom game mode or my previous forge map which starts you out with Shotgun+spike grenades, but for some reason I continue to spawn with this loadout on a new map. I deleted all my custom/forge maps and still have this problem.
Any tips on getting a completely clean, brand new start on a map edit?
i have found that issue also. Now I know you are not going to like I am going to say.
What I have done if I hit ctrl+ s to save it will not save all the changes, So what I do is copy the map and give it a different name. Then I get out of the game completely then boot the game back up and edit rename the map I was working on and it works.
A person forging a map should not go thru that crap editing the map. Also Forge did crash a few times while editing.
Peace! 
this helped! I dropped it for a while since I was so frustrated. Hopefully it gets ironed out post-beta (along with the custom browser)