what are possible causes for automatic transmission shifting hard fluid is fine

You have to have diagnosis from trans shop or call Them and see if u need a filter or flush or something..

I had the same problem on my 1991 190 2.3, I change the fluid and filter, but I still had the same hard shifting. I drained 24oz from the transmission and added "Lucas transmission fix". My Mercedes now shifts alot smoother and my head is not thrown forward from 1st gear to 2nd gear!