Hi Richard,
We've haven't any machines new enough to compare for you unfortunately. Our newest 5008s is about 3 years old but I haven't seen that problem before. Is it the same outcome when you do a front fill degrease too? Just curious!
Would seem strange that s01 works correctly at other times though if it was knackered?
May be worth seeing if Fresenius will provide you enough of them for you to do a batch replacement for any of your machines with that build code? Have you had any feedback from them about it?
Worth asking the question if you haven't already.
Ian Wilde