[0.16.51] Toolbelt rows swapped after loading game

[mattias]

I've noticed an infrequent but recurring bug - after loading a game, toolbelt rows are swapped. Top row is moved to the bottom and bottom to the top.

See attached screenshot - obviously I had locked items in the top row for fast 1-5 and shift-1-5 access.

I am running Factorio 0.16.51 on MacOS 10.13.6 right now, but I've noticed this happening infrequently on many previous versions. All mods are disabled and have been for this save from the start.
I have not been able to find a consistent save or series of steps to replicate it. Saving and loading usually works fine, both when keeping Factorio running or restarting Factorio/Steam in between. But about once a week the bug shows up.

[Loewchen]

Press X

[mattias]

Oh no, never noticed this shortcut. Maybe I accidentally pressed it.