Feeling the chain pickup* in one gear only - Why?

• I think that it was it is.

Got a 12 speed on the eMTB, few months old. Noticed today I could feel what I think to describe as the chain pickup through the pedals. I can only really feel it in 4th and at low rpm. I can hear it slightly as well.

Is something wrong? At first I thought there was an issue with the TQ motor but seems to only be that gear.

It is a consistent feeling, have I damaged the sprocket maybe?