I'm intrigued by that Sanitaire, can you pull up a picture of the brush roll?
The royal has this little black “button/nipple” that sucks in/down when you adjust the vacuum to the correct height. My guys said they were having problems adjusting it. I took it in our old shop, adjusted it really high, turned it on and began lowering it till the button sucked it.... IT NEVER DID.... I smelt burning and shut it off to find a burnt beater bar shape in the carpet. Evidently the little spring loaded button was clogged with dust, etc...Wow. How did you manage that...
I cleaned the button since but still doesn’t suck in. Hell of a vacuum and super powerful but to much adjustment needed too be used residentially.