You may need to really brush out the impeller chamber, it may be that something as small as a grain of sand has lodged in the volute. I regularly take a brush to every component of a HOB filter including removing the impeller and really scrubbing out the chamber.
It may be, from your description of having to shake the filter over time, that something has got in and scoured the impeller making it wobble which can cause wear and cavitation (a crackling, grinding sound) and as Gourami Swami said, the need to replace the impeller or volute may be what it takes.
Although the cost of parts sometimes makes just buying a new filter cost effective.
On the pump impeller below, a few grains of play sand got in (I now never use play sand) and ruined the impeller shaft.

For the pump, the impeller was around $30, but a replacement pump over $100.

Below (I know its hard to see) a wobbling impeller carved a fig 8 on the pump chamber ruining the entire pump.

and below a snail caught in between the impeller and volute, ruined the volute