Game freezes up when attempting to click on an inserter to open the config menu.

IF left alone game will resume but when any action is performed such as adjusting pickup and drop locations game freezes on every action.. Game will crash of there are any keystrokes including mouse action during these freeze periods

I was getting something similar where the error was saying that 'inserter' was nil
I fixed this by modifying the mods control.lua.

I added a check to see if the player.opened or the player.selected exists and that it is an inserter, anywhere set_arm_position was getting called.

Code:
If it's setting inserter by player.selected, no modification needed to the line below. If setting by player.opened just switch 'selected' for 'opened'.
if it's not being called from an event function (on_..._) no need to check the event stuff, unless event is being passed, in which case this is fine.

"if event.element and event.element.valid and player.selected and event.button == defines.mouse_button_type.left and not event.control and not event.shift and inserter_utils.is_inserter(player.selected) then"