Seriously, it's probably from the bubbles. No matter what you do, with cooked custard there are always lumps, and I hate lumps. They're just egg protein that clumped together but I prefer a smooth drink. I usually strain them out and let my dog have them when I'm done.
Last night I ran the whole batch through the blender and it came out smooth and a little bubbly. Well, the small cup I tasted this morning was smooth, anyway. It's also light and fluffy, rather than thick and heavy enough it can be eaten with a spoon. It tastes wonderful, no matter the consistency.
Now all I need is a dish of my grandmother's Poor Man's Pudding. :) Made from leftover buttermilk biscuits rather than stale bread, and absolutely without raisins or you'll incur the disapproval of my brother. Lol