I have an older Suntour 7 RD that won’t change to the smaller cogs. It shifts up fine, but shifting back down it “gets stuck” on the middle cog (5 speed freewheel). I tried adjusting the H/L screws, but that doesn’t appear to be my issue. I thought maybe the spring was shot, but it seems pretty lively when I remove it. Any help or insight would be appreciated.

FYI - This is a replacement RD for the stock Simplex that came on a '72 Raleigh Grand Sports that I restored a few months ago.