Sorry to hear that James.Quite the contrary to my experiences,over many years dealing with the SOTA products.
FWIW,the series IV update is to better isolate the motor/mount,and adds significant damping to the sub-assembly.I had the series III and felt the series IV was clearly better.ALL my motors ran flawlessly,over the years.
One thing folks have to understand is that Sota is not a huge company,like many other high end mfgrs,so it cannot be easy to meet time constraints if certain factors occur.Like parts back-orders.Sudden increase in orders from a good review,etc.
I know Kirk(the owner) is a very dedicated guy(to his customers)and he tries to satisfy everyone...to the max!!Any issues should go through him.He has been extremely approachable from my perspective,and makes a fabulous product,in the long run!
Good luck.