Yes, isolate both it stops. Isolate hot only and it stops. Isolate cold and it pulses. All the pipe from pump to shower valve is visible in cylinder cupboard.
Strange one.
Stuart Turner Showermate, supplied by customer, fitted March last year.
All was well until August when they contacted me to say there was an issue with it pulsing when the shower is off.
I don't believe in coincidence, but at the same time as the issue arose they were having an...
i use a spreadsheet in xl to list out materials + % then estimate number of days/hours to do the job, add a bit on and that's my price.
Gets easier with experience and also if you log materials and time actually used to compare back to your estimate.