Poor jet pressure

Hi, impressed with the help and advice you have offered and hoping you may be able to assist me?
I have a passion superior deluxe spa (same as a grizzly spa). It operates with an LX WP300-11 two speed pump motor and a basic Balboa control panel. We have regularly changed the water but not the filter as we have never noted any need to renew it as water is always clear. We noted a high pitched tone from the water passing through the intake in the bottom of the spa that went away as soon as you put a toe in front of it! I am guessing now that this may have been because the pump was struggling to draw the water through the filter bowl so was drawing at a higher rate from the base of the spa? Anyway… it’s been like this for ages and no issues other than the noise. We then noticed that the electricity consumption had increased by around 30% each morning so the spa was using more than usual overnight but everything still functioned ok. The water level did get a little low at one point and dropped below the highest jets which covered them when we were in it but would have been low for the filtration cycles. It never dropped lower than exposing a jet or two. When using the spa and after it had been running for some time, we noticed it had started to make a loud noise (a little like a chinook helicopter passing overhead!!) and the jets had stopped jetting water out with the normal pressure behind it. The noise sounded more like it was coming from the area of the intake pipe to the pump rather than from the pump itself.
I figured a simple drain and refill may help in case it had developed an air lock, (I refilled by garden hose in the base of the filter bowl as advised) after purging the pump a few times the noise and poor performance remained. I read that perhaps the pump capacitor may have failed resulting in a lack of 2nd speed performance so replaced it with a new one but the fault remained although the electric consumption seemed to return to normal. I have removed the pump to ensure there are no restrictions to the impeller and confirm it rotates with ease when pushed with a finger. I stripped the pump and although nothing smelt burnt or displayed signs of overheating there was signs of the contacts in the end cap being black/burnt. The bearings seemed ok and there is no abnormal noise from the pump itself. On reassembly and refitting the noise seems to have decreased a bit but the output at the jets on high speed is still poor. The spa has a flow control so the water pressure can be split to either side or shared to both sides, when set to one side only the pressure seems normal but when split over both sides it just doesn’t perform as it did.
My thought is that the capacitor failing may have resulted in the pump then suffering an internal fault resulting in a poor output? Perhaps not spinning as fast as it should therefore not delivering at the same rate? It is a little like there is excess air in the system but I’ve primed the pump over and over and can’t believe that there’s still air trapped? The jets are all turned on and they seem to pulsate with the little pressure they are delivering.
Please do share any advice you can offer as I’m thinking I need a new pump but would like to try any other options if there are any you can suggest? thanks in advance for taking a look at this for me, Kind regards Wayne