Low flow warning on control panel

[Debbie Suffolk]

Hi I have a Mars hot tub, supplied by superior spas 15 months ago. we use natural water treatment which is brilliant at keeping spa water clear with no skin iriatation. However we keep having a low flow problem.
We clean the filter every week. We've used white vinegar as suggested by our treatment provider,
Very hot water and have tried a standard filter cleaner and even diluted bleach.
Does any one have any ideas what might be causing this pls?
It's only a 660litre tub running on 13amp (plug and play). The water is filtered before being put in and the water can stay  in the tub for up to a year using this enyzme based treatment system.
I've used s scale removing product occassionally but still get scale deposits in bottom. Any ideas pls?
Thanks

[Hottubprosne]

Are you sure there is enough water in the tub? It happens a lot that the tub runs fine on low but when kicked to high speed it will suck in air and if the tub is heating it will code out and shut off.