Saniflo works in short burst when not flushed eg in night

That sounds like the issue. Saniflo provide them, so contact them for a free one. Article says it is inside the pressure vessel.

Saniflo Saniplus Capacitor, 45 Microfarad - SanifloStore.com

https://saniflostore.com > Saniflo-Saniplus-Capacitor-45...

This replacement is slightly more involved as you have to open up the pressure chamber, once there though it is two small screws on junction box to release ...

More here

https://www.google.com/search?q=replace+saniflo+capacitor

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Contact saniflo sounds as if pump has stopped" working

Contact saniflo

I worked on a lot of Saniflo products, they do not recommend using any products that have bleach or chlorine. Make sure the flapper inside the side inlet where the bath drains, is not obstructed.

I know nothing about the Saniflo system but I suggest you check in the supplied literature if any routine maintenance is recommended and if so I think it would be wise to do that before looking for further explanations (problems).

pipe is frozen wait for it to defrost save some money

Need to check the flapper inside the toilet tank. this is what opens when you press on the toilet handle. you may need to replace it or replace the whole flush valve assembly.

indicates perhaps a faulty pressure switch. otherwise: this happens often in hard water areas due to build up of limescale. Use a descaling agent (acidic) to clean the saniflo - can be introduced via the toilet bowl.

pump keeps running - again this is indicative of a dirty / scaled saniflo. You need to clean / descale the saniflo. if this does not work then an outlet pipe blockage (22mm) may have occurred (unlikely if the unit is operating ok). Saniflo sell their own cleaner, which can be introduced via the wc bowl. If this does not work, then its time for a proper clean ( remove unit, jet clean, acid descale, wash, replace). Obviously not everyones cuppa tea.

Shut down the power and pull the pump from the unit and give it a exam. There might be something as simple as a item that was flushed down the toilet (pencil, pens, combs, etc.) or just a hair clump. Check that the float is free to track fully up and down. Good Luck!