Originally Posted by cubewheels

The downshift issue can be solved by inserting paper spacers between the cog you have difficulty downshifting to and the next physically bigger cog.

You make paper spacers with bond paper and using the original plastic spacers to cut spacer shapes on the paper and finally putting small drops of light oil on the paper.

Begin inserting two piece at a time until the downshifting to the problematic cog and also upshifting from it becomes smooth.