Okay, here is a big dumb mistake. No lives lost or anything, just annoyance on my part for my family.
So, for the last few days I had noticed my tank would not not balance the overflow and return. Mind you, the return is in my basement, so lots of running up and down came with this issue. It was loud and sucking water, it was overflowing into the emergency drain. Alternating like crazy at weird times, no consistency. Nothing I did on the gate valve would last long.
So, today, I went down to investigate as it was driving me crazy. I had been dealing with the 40g/20g so much that it was not a first priority.
Well, a few days ago, I had put a sponge over my intake to the return strainer. This was because of some debris I was having moving around stuff in the sump. Well, I was suppose to take it off when done messing with stuff. Yep, totally forgot.
This stupid sponge was on for days. It was so clogged, I am surprised it was working at all. So, the tank would gradually fill, then drain, then fill, then drain, oh goodness my husband was ready to drain the tank completely.
So, I removed the sponge, now every thing is almost back to normal. What a dummy. I totally forgot I put it there. I hope my return pump is not too hot and run down. Restricting water in is never a good idea.