In the last 20 years or so I have had a lot of Motorhomes towing Toads pass me.
To be fair I would estimate 75 percent or more were towing 4 down.
Having said that I do not recall any on a tow dolly that were swaying.
But I have seem many 4 down that were swaying to the point it was scary but most of the Motorhome drivers would not pay attention to me trying to signal a problem. Some times they would be passing me when I was towing a 5th wheel and I was not able to catch them to try and inform them of a problem. (they were going close to 80 mph and I will not under any circumstance tow a trailer that fast) Even saw one where the front wheels on the Toad was full turned to lock and front tires smoking.