Latest update (sorry to resurrect a week old post):
Put a support ticket into Akai/InMusic right after my previous post (above) on December 18. Still haven't heard back from them with an actual support reply (9 days later). Yesterday I did get an email survey from Akai/InMusic asking how their support reply was LOL.
Is Akai/InMusic support really this bad or is it just the holidays? The first time I put in a support ticket back when I first bought it in April 2019 I got a reply within 48-72 hours. Simpler question that time though.
Anyways, after a few days of no reply from the company I took matters into my own hands and found the link to download the full Internal Memory reinstall ZIPfile (9 GB zipped, 11 GB unzipped) that another forum member posted in another post on this site. Downloaded and copied to my 32GB SDCard and booted up my MPC X. It started the update/copy files process, which only took a few minutes. Funnily enough that was displayed upside down on the touchscreen while it was updating. After it was finished updating I still had issues.
Next I tried deleting all the internal memory content/folders. Including the 3 expansions installed (Vault 2, Essential Instruments 2, Clips). Then restarting the reinstall process with the SDCard. This time it took 15-20 minutes before being done. I thought it was fully installed but no, only about 1/3-1/2 of the Vault 2 content was copied from the SDCard to the internal memory (none of the Essential Instruments 2 or Clips content got copied). Still had playback issues with the demo songs.
Finally, I figured what the hell, I'll delete everything AGAIN off the internal memory that's visible (i.e. any content that got reinstalled). I then used the MPC software to copy/export over the 3 expansion packs (Vault 2, Essential Instruments 2, MPC Clips) to my installed 250GB Samsung EVO 860 SSD drive, along with the 13 demo songs/styles. I then proceeded to play through all 13 demos (loaded from the SSD, not the internal memory), without once getting a hiccup or other error.
Long story short: at least in my case, I think my MPC X's 16GB internal storage is partially defective. The OS/firmware is obviously still on there and seems to be running more stable than it was before I deleted all the add-on content and put it on the SSD. I know several other posts here have mentioned that it's not a good idea to delete the factory installed content because it might cause errors. But in my case it seems as that as long as it is visible somewhere (i.e. internal SSD or HD, USB, SDCard) that it will be recognized and indexed and hopefully not cause stability issues.
The true proof will be when I retest this again this weekend, playing all 13 demos and some demos from the other downloadable content we get from Akai's website for purchasing the MPC X/Live. If it's still behaving stable I'll consider my problem resolved and I can start confidently working on my own music tracks.