Concertina/flynet cassette blinds

Our 2012 Swift Challenger has these blinds.  They have gradually become harder to slide, despite lubricating the side rails with silicone spray.  I have had to remove and repair one blind twice - the moulded slider at one end of the finger rail (between concertina and net) becoming dislodged from its location in the rail. When raising the blind fully up, I have found it necessary to put my fingers around the concertina section and grip the rail from both both sides.   If the rail is moved by placing one's fingers in the recess that is for this purpose, the rail tries to tilt over puts a strain on the push-in joint between rail and sliders.  I am considering changing this blind for one with separate flynet and night/sun blind, and it will cost about £80 with DIY fitting.  This would make changing all the blinds a bit uneconomical considering the value of the van, so it will only be a change where a particular blind (and hopefully no more give up the ghost) when it fails.  To anyone meeting the same problem and needing to change a blind, I would advise them to go for a cassette unit which has the fly net and night/sun blinds as separate items.