I've had my HRX217KVKA s/n MAGA-1441496 for more than 15? years. Other than not initially filling it with oil (the dipstick showed full when I pulled it out prior to starting, it 'seized' to a stop, I filled it up then), and it not wanting to start when cold (I think its float sits too low in the bowl), I've had zero issues. I've done no maint other than oil, and filter cleaning, with one new air filter in all these years.
I haven't flipped the mower over, to clean underneath, in a few years, but there were no cracks at that time. I have a very rough lawn, never been rolled in 20+ years.
The variable speed transmission still works like new.
Oh-and I have always bounced the mower back and forth, to clean out the grass sticking underneath. I guess I'll stop doing that!