Minecraft Version: 1.10.2
Inventory Tweaks Version: 1.61-58

I'm playing on singleplayer
When pressing R, items go all over the place and sometimes just get deleted.
Can't really reproduce the bug but can provide a modlist https://paste.ee/p/fsDzX

Don't know if this helps, but I have also had a similar issue with items vanishing on sort.

Running:
FoolCraft Version 2.5.1
Minecraft Version 1.10.2
Forge: 12.18.3.2511
Inventory Tweaks Version: 1.61-58-a1fd884
JEI Version 3.14.7.420

Upon sort, some items look to appear in my 2x2 inventory crafting but are actually just ghosted (generally an item under the mouse pointer). Equally some items also look to ghost within my inventory, on occasion they will ghost over the top of another item, at which point the item is lost.

The log doesn't look to suggest any error or complaint with regards to inventory tweaks but I do see JEI complaints. After looking through my key binds I see that "r" is bound to both sort and show recipe in JEI. Not sure if that matters, I have replaced the bind to see if I get any further issues.

Many thanks

I am getting this same error. It also tend to dupe other items when it deletes some. Ended up 5 items deleted and 5 Illumination Wands appear in the chest. Also, I am getting this error in the chat log when I try to use the side buttons;

InvTweaks: [ERROR] [3] Failed to sort container: null (l101 in HandlerSorting.java)

Same version as above, using the DW20 pack.

I would avoid using sorting much in creative mode, outside of creative mode it should be impossible for items to be truly deleted as it uses the same code as manually clicking.

Sometimes things go out-of-sync and appear to look weird, but those can be resolved by forcing the server to refresh your inventory.

This is not occurring while in creative mode, at least not for me. This is happening in survival mode. And no, it is not a simple out-of-sync issue. Even restarting the game does not make those duped items return to their original items.