For future generations, I started testing all mods I have one by one and found the culprit:

Picker Extended + Pickter Atheneum - that's what does all the good things with ghost autobuild and has this bug.
Sorry for confusion , will ask them about it.

OK I don't get it. I ran a version with no mods and it doesn't happen - but it's worse, hovering a belt over a ghost doesn't built it at all. I thought that this was vanilla behavior when I hover an item over its ghost it auto-builds - it doesn't?! So then it's one of the mods I just need to find wh...

If vanilla means no mods then no - but I can try, I'll uninstall all mods and try, or use fresh .zip install. Will let you know.

Hi, I noticed an annoying issue with blueprinted/ghosted underground belts. I'm not sure if it's a mod thing or not but I don't know how to diagnose it - perhaps it's a known issue? What happens: 1. When I place a matched pair of undergrounds (non ghosted - belt in hand), all works OK. 2. When I put...

Hi, you are lovely people. The chests were deconstructed (against my intention) so indeed there was missing cargo space. I replaced storage chests and they move stuff back into them. So here's what I think happened: - I had space in inventory - I had unused storage chests placed around the area - ro...

Hi fellow Engineers :) I've been trying to scale up a base into a rail-based megabase for the first time and I'm having some annoying issues with construction using robots (blueprints/copy paste). Can you help? I have dozens if not hundreds of robots that sometims get stuck in the air with cargo, th...