I saw the videos. I would not let that guy on my machine for two seconds.
The hydraulics seem to be operating correctly and well. You can always install restrictors in the different hydraulic circuits to slow down the action because they can be quite touchy.
I'd be willing to bet the engine oil and filter have never been changed, nor the hydraulic oil and filter, or the transmission and final drive oils. Greased every day of use??
Dozers require a lot more regular maintenance than the wheelies, and they are designed as ground engaging equipment so they are slow by comparison.
The Yuchai dozers have some inherent design flaws, IMHO, but nothing serious, just annoying and some are just stupid, er not thought out.
Yes, they are back in production.
Remember, they are not a Cat, and that is reflected in the price, but you can expect an honest days work from it.
I have a root rake for my blade, makes felling trees up to about 5" a breeze, sorry, no videos of that.
I purchased mine with the optional FEL, but I don't use it anymore - opted for a skid steer.