Hello!
I'm hosting a game with my friend together and I added your mod to your mod pack!
But whenever my friend presses Shift + F on any inserter it crashes. We are using Krastorio 2 + Bob's adjustable inserts pretty much. I'm able to use the mod without any issues but whenever he does it both our games crashes!

Do you have a stack trace of the error, it should be in the log file (%AppData%/Factorio/factorio-current.log)?

70.971 Error MainLoop.cpp:1391: Exception at tick 26602553: The mod Quick Adjustable Inserters (1.1.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event quick-adjustable-inserters::qai-adjust (ID 219)
inserter-throughput-lib/vector.lua:259: attempt to index local 'left' (a nil value)
stack traceback:
inserter-throughput-lib/vector.lua:259: in function 'dot_product'
inserter-throughput-lib/inserter_throughput.lua:1116: in function 'estimate_extra_pickup_ticks'
inserter-throughput-lib/inserter_throughput.lua:1192: in function 'estimate_inserter_speed'
quick-adjustable-inserters/control.lua:2301: in function 'estimate_inserter_speed_for_inserter'
quick-adjustable-inserters/control.lua:2318: in function 'update_inserter_speed_text_using_inserter'
quick-adjustable-inserters/control.lua:2397: in function 'update_inserter_speed_text'
quick-adjustable-inserters/control.lua:2738: in function 'switch_to_selecting_drop'
quick-adjustable-inserters/control.lua:3391: in function 'advance_to_selecting_drop'
quick-adjustable-inserters/control.lua:3405: in function '?'
quick-adjustable-inserters/control.lua:3457: in function 'adjust'
quick-adjustable-inserters/control.lua:3838: in function <quick-adjustable-inserters/control.lua:3825>
70.971 Error ServerMultiplayerManager.cpp:92: MultiplayerManager failed: "The mod Quick Adjustable Inserters (1.1.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event quick-adjustable-inserters::qai-adjust (ID 219)
inserter-throughput-lib/vector.lua:259: attempt to index local 'left' (a nil value)
stack traceback:
inserter-throughput-lib/vector.lua:259: in function 'dot_product'
inserter-throughput-lib/inserter_throughput.lua:1116: in function 'estimate_extra_pickup_ticks'
inserter-throughput-lib/inserter_throughput.lua:1192: in function 'estimate_inserter_speed'
quick-adjustable-inserters/control.lua:2301: in function 'estimate_inserter_speed_for_inserter'
quick-adjustable-inserters/control.lua:2318: in function 'update_inserter_speed_text_using_inserter'
quick-adjustable-inserters/control.lua:2397: in function 'update_inserter_speed_text'
quick-adjustable-inserters/control.lua:2738: in function 'switch_to_selecting_drop'
quick-adjustable-inserters/control.lua:3391: in function 'advance_to_selecting_drop'
quick-adjustable-inserters/control.lua:3405: in function '?'
quick-adjustable-inserters/control.lua:3457: in function 'adjust'
quick-adjustable-inserters/control.lua:3838: in function <quick-adjustable-inserters/control.lua:3825>"
70.971 Info ServerMultiplayerManager.cpp:816: updateTick(26602553) changing state from(InGame) to(Failed)

thank you very much, I'll look into it

This should be fixed with Inserter Throughput Lib 1.1.1