Stacking: partial stacks of some items will not combine into full stacks. The example I tested was solvent. I have five stacks of solvent that are all under 100 units. All five stacks have an Item ID of 617597. If I drag a stack of 68 on top of a stack of 58, they will simply swap locations in the bag rather than stack together. This happens both in the main inventory window as well as the utility pouch. I also tried it in a Gataroskin bag as well, same result. I am in Isle of Dawn, I bought the solvent at Isle of Dawn from one of the crafting supply vendors (can't remember which). I have also observed the same issue with Weakened Logs. Both of them have item ID: 911459, neither stack has a crafting grade associated with them, and a stack of 96 will simply swap spaces with a stack of 95. The log stacks I was only able to test in the main inventory. Also I checked the stacks of solvent, and none of them have a crafting grade associated with them either. Hope this helps.