Danfoss Lockshield valves leak after adjusting

[StillGame]

Heating system is 14 years old. On inspection I find that every lockshield valve is fully open. After adjusting some, I find that they weep slightly from the adjustment screw - valve type is as in attached picture, with only the adjustment screw behind the cap. Leak sealant is in the system - do I rely on this to do its job or is there another tip to make them seal better, or do the valves need to be replaced?

 

[ShaunCorbs]

Replaced but they might seal up over time