Oh, wait... Setting to 8 should give 120 item/s. (As speed 1 refers to the basic transport belt of 15 item/s.) And my allowed maximum value is 12 (180 item/s). How did you get 360 item/s???
I am still on 1.1.6 (as I am not updated to 1.1.11 yet), but I do not believe the vanilla game is taking such a radical change in mid-version. Are you using some other mods that also alter the belt speeds?
Secondly, there is no surprise loaders are not working at 360 item/s (no matter which mod is responsible for altering it).
As I have already stated on my mod main page:
- (Tested on game version 0.18.30) Scale 8 (120 items/s) is the maximum speed for any loaders, due to engine limitation.
I believe this statement still holds (at least up to 1.1.6), as the devs have never updated the loader limitation.