This is a reproduction of MC-230235. Since this MC-230235 is set as private, I opened this issue

Reproduce in Vanilla Server + Vanilla Client!

I have successfully reproduced this bug on Vanilla client + Vanilla server, Need higher network latency, so I use vpn to make ping reach ~700ms: https://youtu.be/As4i8oEc9W8

1. Make your network connection with the server have a higher delay
2. Make sure there are 8 sets of diamonds in the backpack, no spaces, and 1 set of diamonds on the ground
3. Hold shift and click twice on the diamond block in the recipe book
4. When the diamond block appears on the crafting table, press Q to throw it out
5. If you successfully threw the diamond block out and disappeared, there should be 8 piles of 126 diamonds on the crafting table
6. Turn off the gui and let them fall to the ground, or you can take them off

Reproduce in Vanilla Server + Fabric Client with Item Scroller Mod

I demonstrated in the video from downloading the official website server to reproducing the bug in the vanilla server

Since it needs to craft items very quickly to reproduce this bug, I used the item scroller mod on the client, but the server has not been modified in any way.

In addition to increasing or decreasing items, it occasionally produces negative items.

 

 I can firmly believe that there is a problem with the crafting item interaction logic

Since the video is too big to upload, I uploaded it to youtube, don’t worry, it’s hidden: https://youtu.be/v_kZcWBWjuo

In this video, I split 9*64 emerald blocks into emeralds, and then made them into emerald blocks, but in the end there were 27 more emerald blocks and 8 emeralds

 

This is a process where I used this bug to generate negative items: https://youtu.be/vw0rSVvAG7w

In this video, I have converted the diamond block and the diamond to each other many times. After each conversion, the number of items I get is different, and at the end a negative diamond entity is formed. I can pick up infinite diamonds from above.

Related in Item Scroller issue

masa should know more details about this issue

This is what masa mentioned in the item scroller issue

They changed some of the inventory interaction confirm packet behavior in 1.17 (I haven't looked at the actual code changes yet). Unfortunately it's now possible to both lose or duplicate items via "regular" slot clicks. I assume it probably needs some specific fast timings for some actions to happen, and that's what Item Scroller is doing - sending lots of normal slot clicks very fast.

I don't think there is anything else I can do to fix this from my side than rewriting the crafting features to use the vanilla recipe book protocol. I don't know if some of the other "normal" item movement features would still have the same issue as well... This should really be fixed in vanilla, and I'm hoping 1.17.1 or some later minor update would fix the inventory packet stuff again. The current situation is obviously very bad, since it's even possible to lose or dupe items via just slot clicks.