I am guessing this is happening when you are desperate for blood? I have found that the blood meter fills, but also drops with time. Now it has a threshold where if it goes over, you can feed, and it can still gain blood at that time. The problem is when you just get a little blood to send it over, it drops back down below the threshold before you can even tap it. This becomes extremely frustrating, because that is when you need it the most. When you are hacking an slashing and it gets over filled, this does not become an issue.

Also, still having the issue where if you let it get to flashing then feed, it will keep up the flashing. Posted these in another thread, but hopefully they will find a way to fix em.