New PRV Fitted to Unvented System and now Reduced Flow

[Mrmichaelsankey]

New here, so be gentle.
Had a new prv fitted on an unvented system. Pressure isn't the issue, but the tank takes and age to refill and when doing this the cold at the prv has reduced flow.
Have another prv on the mains inlet. Can't tell you the pressure it was at, but it was quite high, as was the flow.
Could the open prv down stairs cause issues causing the prv up stairs to close this reducing flow?
Thanks in advance, Mike