It appears to me that the chain is contacting the spacer between the 11 and the next larger cog. This is not the hub shell. That should not be happening and can only mean the chain and the 11 cog are not compatible or worn out. If you have the wrong lockring on the cassette it could explain chainskip on the 11 but that would not explain the chain contacting the spacer. The 11t cog must have the special 11t lockring.
I do not think derailleur adjustment is the primary problem.
Be sure to measure the chain for stretch. A 24 pin interval of new chain measures exactly 12 inches. By the time any 24 pin interval measures 12 1/16 inches it should be replaced. If you replace the chain and the skipping continues you probably need a new cog and maybe a new cassette. Do you really need an 11?
Al