Buying two poachers; after completing the first, the second will not stack; has to be rebought

Had a game where I bought a poacher's dirk. It had one stack remaining on it. I was doing a good job counterjungling, so I thought I would buy a second, so i could get stacks on the next one after completing the first while in the enemy jungle. Of course the second one didn't stack while I was completing the first; no surprise there, working as intended. But after completing the first poacher's dirk, the second one did not stack. I had to sell the second one and buy it again. After that, it would stack.

Prior to 1.10, I could have two poacher's dirks in inventory, and the second one would start stacking after I completed the first one. Somehow patch 8.10 introduced a bug into how poacher's dirk stacks.