I have this suntour derailleur on an old mtb. when I shift to the bigger 3 cogs the jockey pulley is no longer engaged and if I shift to the biggest the chain rubs the cage and sometimes finds its way out if it.
it seems the derailleur should be pivoting forward more so that the jockey stays engaged with the frame. but the tab on the rd is flush up against the tab on the hanger so it cant pivot further.
here are a couple of pictures. axle wasnt all the way into the drops in these shots, fixing that helped some, got the pulley fully engaged on the 4th biggest cog, but problem still exists on larger cogs.