Extremely low hot water pressure/flow via Thermal store

[speccy]

The issue is the hot water initially has some pressure then slows to a very poor flow less than gravity fed before we switched to Thermal store (of course theoretically mains pressure hot water)

In the cupboard with the thermal store we have a Caleffi mixing valve. If i turn the dial to max the water is hot but trickles out slowly at the tap, if i turn it to 5,6,7(7 being highest before max) the water is flowing out close to mains pressure but almost cold.

Thermal store mass is about 78 degrees currently and the pipe from the TS to the Caleffi mixer is fking hot so it's not cold.

This worked fine last winter so i don't think its about the low water temp going in causing the output to be lower in turn causing low flow.


This is what the mixer looks like, is it this failing?

https://store.heatweb.co.uk/product...Ng2u5lcnvNnwasLmfRHEPuqoLukifpoRoCeI4QAvD_BwE
Help!

 

[speccy]

OK i found my issue what is this?!!!! Looks like a massive buildup of limescale its green though like it's reacted with copper? Only just over a year old since this was fitted

https://ibb.co/BNqKwCV

 

[Ryler]

Thermal stores make lime scale for a past time.