We have a Newteam 8.5kw shower which is losing pressue over the last few weeks( spray getting less) The temp setting has been the same since installation and this issue is a new fault. Checked mains water and this seems normal ta the taps. If temp settinf is lowere then the spray increases.

Did you try to remove the shower head and run water without it ? Is the pressure / water volume better ? Did you try to clean shower head ? ( there is a small filter screen that may be clogged up )..

Back to you / Milo