I had the exact same issue on a Hik dome cam on my house.  I swapped it out for another camera and all was well there.  I sold it at a discount to someone with an explanation of the issue and we installed it inside.  It has no issues with IR.  I think it is likely the dome was not seating correctly against the lens surround when installed on my house and now it is.  No other explanation for why it is ok now.