Ideal isar HE24 leak at bottom

[dan4738920]

 

[dan4738920]

Hi...15y old ideal he24 boiler, only had one repair from BG 2y ago, the heater exchange replaced and minor leak washers fixed, been 100% all the time no issues, used daily.

Noticed today a slow leak, 1 drop every 10 seconds from marked area in picture. (you can see the drop under the black circle plastic part.
Anyone have any idea what it is, boiler is working and so is CH no tripping but want to work out if its worth fixing it just cant figure out what it is?
When I drained the boiler, the leak did stop, the leak water is warm not hot or cold.
Thanks

 

[dan4738920]

Just more pictures. where the blu tac is ( just to show Im not trying to fix it) thats where the leak is... and second picture is another view...seems to be that black thing connected to the heater plate leak...anyone know?