Reproduction Steps : Only needed scarecrow bug to be fixed. To be sure I did the achievement I always freshly craft each item and put them in boxes in order. After finishing the last items the DIY still didn't pop.
Repro Rate : I've only made 1 extra set of each item (as it's expensive and time consuming) but it's also why I keep all the needed items until needed.
Game Platform :Steam, PC
Game Version :v1.1b-1235
Input Mode : Controller
#DIY Expert
forest kettle
dim girder
Hiyaaa @forest kettle. Thanks for reaching out to us about the bug. We'll let the teams know about this and get back to you again! 
dim girder
Hi again @forest kettle. We checked your save file and there's a possibility that you might have missed crafting a few items. We tried re-crafting everything, and that successfully triggered the DIY Expert achievement on our end.
Can you try re-crafting every item again and see if it unlocks for you too? Let us know how it goes! 😊
forest kettle
...I fresh crafted everything in those boxes, as they went into the boxes. The items never placed on on the map. Re crafting EVERYTHING is a ton of materials that I already used to craft those boxes... is there certain items saying not made by me somehow?
dim girder
Do you happen to have a video of you crafting each item from the crafting list? It would really help us investigate why the achievement isn't triggering! 😮
forest kettle
No, because it took me a few days irl. I had to do a lot of smelt and gather, and catch a new cricket. But I would craft each item and put it right in the boxes in the same order as the crafting menu so I could be 100% sure to have exactly 1 of every item. I have boxes with 1 of everything for the other achievements too.
forest kettle
Despite the wasted resources, I did re collect and recraft everything for the DIY. The achievement only triggered after I crafted the last item the Ultimate Scarecrow. Which means I really did unnecessarily craft 2 sets of everything as I have crafted at least 8 of those (4 on land, 4 under water) and I assume the achievement would pop after you craft the last item needed.