Saggy Dropper (tranz x ) options please

My sons Tranz x 200mm dropper has developed a bit of sag , so wondering if anyone has any top tips, fixes or is it a replacement. If so is there any cross compatibility when looking for a new cartridge. I was lead to believe that trans x made a lot  of the droppers on the market so that might make things easier.

Thanks

I know they also make the Brand X so perhaps the cartridge is cross compatible?

Is it the fixed 200mm model or the 170-200mm adjustable max travel?

Are you sure it’s the cartridge? The first place I’d look is the cable, as the cables get sticky they can hold the valve open occasionally. So replacing the inner and outer cable first may be a cheaper option?

Has he manually raised the seat? That tugs on the cable.

Yeah its the 200-170 adjustable one , he stripped it last night but I will get him to check again the cable operation and maybe try without cable to eliminate that. He is pretty careful about not lifting the bike by saddle as we used to run reverbs and that would sometimes mean a full rebuild . Does lifting by saddle cause issues ??