DC Pump Inconsistent Performance

[Boostable]

Been running a set of Wavelike DC pumps on my tank since June. A DC4000 for my skimmer and a DC10000II for my return.

Out of the gate pumps performed beautifully. I ran the 4k at about 80% and my 10k at about 70%. I fully expected to see some flow loss over time due to the things I have read but it would seem these pumps are inherently inconsistent from cycle to cycle as well.

For example. On the 4k, it started to fall off a little a few months in and I dialed it up to compensate but on top of that I began to notice periodic flow changes after feed cycles, maintenance, etc. Not drastic but noticeable enough that I would need to adjust for it.

Now the 10k has been a little more consistent (gauged by my overflow level) but I have had to dial it up as the output has decreased. Just one click up to about 75/80%. But does require me to adjust the return from time to time.

Also the fan on the 10k controller is about to crap out, but that is another topic.

As of last week I was just not happy with the skimmer performance (decreasing) so I pulled the 4k completely and replaced it with an old mag9.5 and it is back up to expected performance.

Has anyone else been experiencing these types of issues with the DC pumps?

Love the low wattage usage but I don't want to be chasing water levels every other day either!

Jack