Sedis Sport 5 speed chain, almost new condition, less than 500 miles
ultra6 freewheel recent NOS addition, maybe 150 miles old
Recently added Superbe Pro rear der, had shop fine tune it, it is straight (well used unit, seller reported that it shifted well in it's previous install)
The chain appears to fit the cogset without obvious visual trouble however…
I have troubles shifting from 2nd into 3rd cog without skipping it to 4th (where 1st cog is 22T). Most often 3rd cog is skipped regardless of how delicately I try.
Similarly from 4, it wants to skip 3, and go right to 2. It’s not like that going from 3 to 2; 2 is an easy shift. However, 4 to 5 is slightly finicky. Such is the case in either ring.
What is the trouble - could it be that I need an ultra6 specific chain?
Could it be that the old Superbe Pro rear der is worn out? How does one diagnose that?