E&B water pump doesnt always engage

I'm not sure what to make of this yet. At yeast twice on separate occasions I have noticed that the timer is on and the water pump is on, but the pump isn't at full force. As such the timer runs out and the water level doesn't rise to the proper level. If I catch it I will reengage the pump again and every time it works on que. Surely though if happened to catch this happen twice it's happening when I'm not looking too. For now I have reduced the watering length to every hour which will catch any missed floods.

So whats the scoop with this pump? I bought overkill for what I needed. It floods my table in about 90 seconds. I think its 550 gph which for a 25 gallon res if sufficient I should think. But maybe I didn't buy one with the right design. I have two of these pumps which I could return if I knew them to be the wrong type or something. I'm using 3/4 rubber tubing and there are no bends or elbows in the line. I'm sure it's not entire straight but when it's working, it works fine. For some reason the pump doesn't always want to build up pressure. Got it at Lowes for like 75 bucks. Thoughts?