Sometimes if a chain is too long, shortening it might help.
A longer bolt might help. The problem with longer bolts is keeping them on the hanger tab.
Some RD’s just have weak b springs. I found that with a couple of Shimano RD’s rated for 34t and 32t had an issue. On one bike I used a locknut on the end of the b screw to gain enough contact with the hanger tab. Not pretty, but it works.
John