Spectra 360C watermaker excess pressure no product

[Tudorsailor]

I have a Spectra 380C that was installed 2001.
The Clark pump was replaced in 2012
I installed a new membrace 4 months ago.

I left the boat 6 weeks ago and pickled in the normal way

After a long flush I tried to make product. However the pressure went off the scale to beyond the pump cut offs. I have checked that nothing is closed off or kinked
I had some advice from Tech Support at Spectra. He suggested closing the Pressure Relief Valve very slowly. I did this and heard a clunk as the Clark pump moved.
Now I can get the PRV almost closed but the pump is clunking too fast and the pressure goes up. The flow indicator shows occasional product 20l/min
The next suggestion from Tech Support was to close off the brine out flow 12 times. I have done this with the PRV open and also almost shut. No better.

Before taking the Clark pump out to send to be overhauled is there any other things I can try???

THanks

Tudorsailor