Shower trap leak

[tellme_why]

Hi,
A wet patch appeared on the newly plastered kitchen ceiling (see pictures). The plasterboard brittle matches the first floor shower drain location.
The Kudos walk-in shower sits on the first floor bathroom.
I removed the shower cover to expose the shower trap (which looks like a MCAlpine make - but not sure of it) and noticed scale built on the trap itself as water has been dripping for a while.
I briefly run the shower to see whether water would drip but no success.
The drain blocked up on a regular basis and I use powerful drain product to remove blockages.
Recently a plumber show me how to clear the drain and since then I did't use the drain liquid any more.
Please could anyone advise how to fix the leak?

Many thanks

 

[dilalio]

Well. Seeing as you have relatively easy access, I'd just change it for a new one and make sure the mating surface is smoothed clear of existing scale.

 

[Madrab]

May just be my eyes but in pic img_9530 the lip of the trap looks like it's cracked, when weight goes on the tray the seal moves and makes it leak, stand in the shower and use blue roll below the trap, if it gets wet replace the trap.

 

[tellme_why]

Thanks dilalio; I hope I can remove the trap rotating and taking it out without need to lift the shower..
Thanks Madrab you are right.. it seems very much an hairline crack that would explain the leak..
Cheers