weep from towel rad bleed screw

Just had a towel rad installed and getting a weep from bleed screw. Not from the screw itself but it's not sealing properly so water coming from the small hole.

I presume I can just close off valves, take out screw completely, wrap a bit of tape and reinsert? Should this do it? Can't understand why these should fail. It's a sonas branded rad.

Failing that the plumber will be called back.