Shadow Blades working at random

So I am running into this issue where: I pop Shadow Blades, then run through a rotation of combo builders (These should cap after one use), and combo spenders. However, I only get full combo points some of the time. About 80% of the time it works, but the other 20% I have Shadow Blades on, and it doesn’t matter whether I pop Cheap shot, back stab, or the rest. I still only generate 1 combo point. Anyone else having this issue?