I have that problem on my Bianchi but only in the 11t sprocket. Change gear and it goes away.

Reckon it is the chain somewhere and just catching a tooth - but not on the cassette- as it is on one revolution of the cranks- it must be catching on the outer chain ring that may be bent But get off the bike- Take the strain off and I can't find it. Chain is up for change in any case so hopefully that will cure it.