Might be stating obvious and apologies if youve done this already.
You mention its a new pole, so taking that as you had a pole before. If so, is the brush still on the old pole? If so connect old pole bk up and see if any problems still exist. If it does, might be suggestive of the pump as some have said. Hiwever if it works well then its not pump.
As above is it a change of jet sizes or extra jets? Again obvious but i went from 2 jets to 4 and a flow from 45 osn digi reader to now using 70.
Are the jets slightly blocked, push a pin in jet holes to clear. Unconnect all pole hose fittings at brush head and just double check the connections/push fits etc.