Except that it is, if you watch Anti's video and see how he's generating a compressed lane. He's compressing the lane with sideloading and electric mining drills, unless I'm missing something off-screen. The inserter is then further compressing the lane later, because sideloading and mining drills d...

If it's any use, I've attached the save I used to reproduce it, which included some additional testing to confirm that the compression issue wasn't just a visual bug. I used the latest version of 'Creative Mode (fix for 0.16)'. It compares smelting (a 48 steel furnace line) between a sideload compre...

It doesn't look like sideloading can fully compress a belt, whereas an inserter can. So the source of this problem seems to be that inserters can insert into any gap in a belt, no matter how small, but sideloading can't. Somebody on reddit put up the following gif demonstrating this which I can repr...

My game similarly crashes with no input and no mods after upgrading to 0.16.17. Potentially similar causes.