Love both these mods, posting this report to both because I don't know which side owns it.

There's a weird interaction between the way Inventorio is handling pickups, and BitsAndChisels is handling large stacks of bits. Basically, if Inventorio has a full stack of something in one of the offhand slots, or in a Deep Pocket slot and then picks up another drop of it, you can push your stack beyond 64. I made a 32k stack of sticks, lol.

The minimum modstack to trigger this seems to be:
Fabric API
Fabric Language Kotlin (inventorio dependency)
Inventorio
BitsAndChisels

Reproduction steps:
single player cheats on
give yourself 128 sticks
put a stack in your Inventorio offhand
throw the other stack on the ground
pick it up
128 sticks

This feels like an Inventorio issue initially, but doesn't happen if BitsAndChisels is off. Likewise, it can't be reproduced with the Vanilla offhand, with Inventorio off. So it appears to be an interaction.

1.19.2/Fabric 14.10

Reproduced this bug in Survival mode without cheats

Weird stuff going on with Stacker; the bug can only stack to the highest amount a different (or the same, but that wouldn't be a bug) item can stack to. Bits and Chisels is not required if Stacker is present to reproduce this bug. May be the same thing going on here, since the bits seem to stack infinitely.
Andrew6rant/Stacker#70

Same bug in Stacker, a seperate mod. This may be caused by a library used by both

Reproduced the bug with only Inventorio and it's dependencies.

Closing this bug on this side. It's become clear this is an Inventorio issue that Bits just makes more obvious. Thanks for the investigation