Hi I'd read before about the low platelets. It could have something to do with the sterilization method.
I'm on Nxstage 6 yrs now, but have always 'tanked' all the gasses out of the cartridge as it gave me asthma attacks. Maybe mention this to the neph, before all this extra appointment stuff?
Nb I 'tank' the cartridge by: load cartridge, connect to saline.
With a 30ml syringe connected to cylinder (blue clamp) withdraw 5 x 30 ml air out
(Closing clamp in between of course)
Press fluid toggle, when the sound stops rising count till 14 (I know this sounds mad)
Withraw 5x 30 mls again.
And finish priming
Here's one article, just google there's more
https://www.ncbi.nlm.nih.gov/pubmed/26521886Lots of luck and strength, Cas