Helo, hope you having a great day.
My game now crashes to the main menu when I place a blueprint with splitters in them, but only of blueprints and blueprint books from outside the save file. Any blueprint which I created inside that save work totally fine. I can even use splitters then in the blueprint.

I also have no Unichest in the blueprint itself, I noticed this when I tried pasting belt balancers on Moshine, it crashes on any planet tho.

Error while running event Unichest::on_pre_build (ID 9)
LuaItemStack doesn't contain key contents.
stack traceback:
[C]: in function 'index'
__Unichest/scripts/main.lua:58: in function 'Inventory_get_blueprint'
Unichest/scripts/main.lua:68: in function <Unichest/scripts/main.lua:65>

I hope my little testing helps. :3

Got the same issue when using this blueprint, otherwise it seems to work.
The very same blueprint worked just fine on my previous playthrough without unichest.

https://forums.factorio.com/viewtopic.php?t=121438

Just blew this one up, also. Trace is identical. The blueprint had been placed a couple of dozen times previously. I was in remote view, but I had already placed it a few times that way just before the blowup.

Unfortunately this issue is game breaking for me since i cant use blueprints and im way to deep into the game to remove the mod :/ will check back in a few weeks or month to see if the issue have been fixed or a work around :(

Thanks for the detailed report. Version 1.0.9 should be fixed. I wasn't able to reproduce the crash, so please let me know if the fix didn't work.

Nice it seems to work now, placed maybe 25-30 blueprints on the first 4 planets and had zero issues, great work.