I... Don't quite fully grasp all the details going on... and Don't know if this will be relevant with the new version.
First. I'd like to recommend not building items until they're requested.
What you can do to alleviate time strain is instead just make the parts, and set them near the order desk and work table. (For version 0.0.82)
This will prevent them from breaking, Regardless of same session or exit/reload. I've heard cases where people saw their items "create" but then within 30 minutes or gameplay (no exit) they thought they were "Broke" like how the "Exit/reload" breaks them.
Side First. - Robo - Try assembling them in a different order. - Being able to grab or have better alignment for where they spawn/how they spawn greatly reduces physics going nuts. - Think If I recall right, the best way to do it was place the tool head, then holding the grip, swipe into it, lifting upwards as its coming into contact and hopefully you should then form the item, and immediately, be lifting it away from the table.... I could be wrong, I put off playing it for quite some time saving up my enjoyment for the new version to come and take.
second. Try to make sure to watch the corner of the screen, and Try and ensure all parts are "Finished"
In .82 and earlier - it wasn't uncommon for one of the errors to be "Heated" despite lack of display or indicator - and a "Heated" tool head can't be used for squat - dunno if it can still be attached.
The easiest way to accidentally fudge this one is when you finish hammering a head, you dip it, but then turn back towards a still roaring forge, it soaks up a minuscule amount of heat, and thus, requires cooling again - but doesn't look like it. Disassemble if you think this might be possible, and drop the head back in the oil.
Alternatively, it could be like I talked about in the First part.
So make sure to watch when assembling to verify if its assembled correctly and "creates" the weapon - I don't think I've recalled the weapon ever actually saying on the grip that it was the weapon - once they're assembled you only interact with grip, to my recollection.... so that part isn't necessarily wrong....
But there are some ways to not make weapons...
a Pickaxe for Customers has a 2h grip and pickaxe head.
This is the only way it will say "Created pickaxe" blah blah blah - and the only one a customer will buy.
But the Player can attach a pickaxe head to 1h or pole grip, AND, can equip them as is, as long as they are "Pickaxe headed" and you select the pickaxe slot, the player can equip it.
Same with Hammers, and hatchets. (I call 1h ax hatchet)
Hatchets can be 1h or 2h grip, if I recall right... Don't know if I ever tested pole - They'll only "Create 1h ax" if you use 1h
Hatchets can't be made with large axe head, no matter what, and the player cannot equip large axe head - only Hatchets.
Polearms offer the most variety.
You can make a "Spear" (variant 1) polearm with small blade, medium blade, or large blade - and you can also make them with guards. (IIRC) (used to have photos of it)
Polehammers I think were only made with small - but I could remember wrong and maybe large hammer head could also make a polearm.
Weapon sales in 0.0.82 were affected by parts specifically, not really type - so that meant when someone asked for a spear, instead of "1 ingot" dagger or 2 ingot hammer - you could actually pump out a three ingot large blade and nice grip, guard, and really bank.
BUT.. I digress... I don't know the full extent of what you're looking at here, and can only assume its related to "during session item break" - and for that, my best answer is don't fully assemble until sale.