Power Steering Weirdness

2011 CX-7
Hi there,

My wife and I drive a 2011 CX-7. I recently tagged along with my wife on a work trip to Vegas, and we left our vehicle in the long term parking at the airport for 5 days.
Since we returned, the power steering has been playing up, and my online searches haven't yielded any direct solution.

Steering becomes increasingly stiff when RPM drops below 1500 and speed below 20mph

Checked the fluid levels, they were slightly low. No change after topping up fluid.
Pumped up all the tires.
Disconnected battery for 30 minutes.
I'm assuming the rack is okay, based on the fact that the steering is fine under power. Is that a fair assumption?

Is there anything I may have overlooked?
Is it possible to test/verify the pump?

Feedback is greatly appreciated.

2011 CX-7
Power steering is almost back to normal.

We went to visit friends over the weekend, who live on a farm with a lengthy gravel driveway. I suspect the rough road helped loosen up the steering.

I say almost back to normal, as I've had a few instances of heavy steering in the last few days and haven't been able to pinpoint the exact conditions to replicate it.