Items won't stack if there's no open slot available

I recently started doing emerald runs at Seavale Reef because Bob's Reincarnation is hard and I need potions. While I was doing a run, I noticed that I had half a stack of coral ruby in my inventory, but additional coral ruby wouldn't stack. I decided to drop a Coral of Nelfors that I was holding (already did Temple of the Legends btw), and then the ruby stacked.

I'm not sure if this happens elsewhere (haven't tried or noticed), but I'm wondering what's causing this to happen.

If needed, I can provide a video of this happening.

 

Here's a video of this happening

 

Yeah happens to me I’m not sure if they can fix it since it’s been like this since 1.19 or earlier, that’s just the version I played on

 

Happens with pretty much all items
I've noticed that if I have a stack of less than 64 emeralds, and the rest of my inv is full, then I can't pick up emeralds

 

Interesting. Any idea if it's due to some quirk in the code?

Also I beat Bob after like a dozen tries

 

It's just due to the fact that Wynn has to process every item going into your inventory, as it needs to make sure that even items with different NBT tags and tooltips can stack. For example, an emerald stack in your inventory might have the tooltip "26 E", which makes it a different item from emeralds you can pick up from the ground. So, it's not going to automatically enter your inventory because they're not the same item. You have to have an empty slot for incoming items to occupy and get processed before they stack into your inventory.

 

I see. Thanks for the explanation