Failing Filter Pump

Hi I have a Aqua Vogue 245ltr with an Ocellaris 850 external pump. I've had problems with flow/pressure i.e. it seemed to be getting less and less. About a month ago it was down to a trickle so cleanedd the impellar and took the pipes out and cleaned them etc. There was a bit of gunk in the pipe but it wasn't blocked. But when I put it all back togther the flow was much better so, I thought job done.
I've just done a PWC and its back to a trickle. I've checked the impellar and the tubes and, apart from one rouge snail all is clear but it hasn't got any better. The water is slightly cloudy, I assume as direct result.
I've had the set up since May 2020,
Should I expect it to have failed after a bit over 4 years?
Any ideas how I might get it sorted?
If not any recomendatrions for a replacement?
Grateful for any advice. Thanks.

Thanks Sue but I do clean the media regualrly, so it still a msytery. I suppose it could be the motor failing but 4 years does not seem much of a life for a puimp that size. I'm, going to strip it right down again but I think a replacment may be the only answer.

I've answered my question, yes they do sell impellers. I've used this company in the past and they've always been reliable.

https://www.fishpetsreptiles.co.uk/aqua-one-parts/aqua-one-parts-by-filter/aqua-one-ocellaris-filter-spares/aqua-one-ocellaris-850-parts/aqua-one-ocellaris-850-pump-head-impeller-137i-

Look on 'fish pets reptiles' site, they stock quite a range of makes.

Anything can decide to stop working. Our microwave stopped working while I was in the middle of using it and it never worked again  If a microwave can do that, so can a filter.

It happened to the pump on one of my filters a while ago. Luckily I had a less powerful version of the same filter from a tank I'd closed so at least I could use the pump from that while I sorted things out.