After dealing with this problem for a while, I concluded that there is a bug in how steam Auto Cloud feature works. It will always report as "stored" whatever is currently in the autocloud folder (~/Factorio/saves for factorio) up to the quota (4.66GB total up to 250MB file size), even if the files ...

I did some experiments, my theory is it related to starting/ending belt on existing belt. Experimented in singleplayer in editor, but used items from inventory.

Experiment 1. Ending at belt. Blue box - belt placed before, red line is where i started dragging belt fast, red arrow is the direction ...

It will also free a key bind!