I downloaded the MGU and loaded it into my DAW.

So I have soloed the piano so I can clearly hear the parts. In my machine, it plays perfectly. No hot spots and no warbling. To note, my machine is well past a decade old. It runs XP Pro 32 bit on the i5 Intel chip and 4GB memory.

I did pay close attention at the places where you indicated you were hearing abnormalities. I didn't hear what you hear obviously. That doesn't mean you don't have a problem, it's just that I can't replicate it on my old DAW.

At this point, you are playing detective to find out what is going on. I'm thinking it's either a setting issue or related to the soundcard hardware and driver.

My question would be... what sound card or interface are you using and what driver is it running? Check that all your sampling rates are set to 44.1Khz Check Preferences> audio and midi driver. Latency and buffers should be set low for latency and mid to high for buffers....or whatever works best for you.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.