Long time reader first time poster.
I have a non ec cem60 and I have had none of the issue stated.
It is mount on a concrete pier (Rock of Gibraltar) and is never moved and settles down very fast even with 15kg on it.
I can slew a to a object and follow it with my eye and it stops near dead with very little ra adjustments saying that I balance it scope heavy.
It tracks well guided and unguided.
I have had issue's with the build quality but not the design.
Mine came with a lose polar scope so you couldn't polar align it.
I pulled it down and fixed it, I also tighten the bearing collar quarter of a turn more than what it was.
My guess its the tripod or pier or just a bad build.