James,I have had 4 different generation Sota Cosmos tables.I've never had the "slightest" drift in speed,and believe "this" is one advantage of the design.Accurate to the 'nth degree!!
Sorry to hear about your problems here.Possibly a worn belt?Maybe the table is not perfectly level?Who knows?I'd certainly call Sota because that should not be a concern.
As to the little "pitch nob"...earlier tables had a small(so what?)nob,recessed in the back "well",where the air hose and ground was.Once again I've never experienced anything "loose" here,and never any "play".Actually,I always thought it had a high quality feel to it,during rotation.
The very latest Cosmos(which I now have)has an upgraded nob(I don't know why,as the old one did just fine)which reminds me of the nobs found on the better microscopes!It is a bit larger,and more refined looking too.
Really a nice touch,but I could care less,as I've never experienced any pitch,speed problems.
Good luck