Thanks for your detailed reply & for the "Delamination site".
I've had a quick read through the information there & was not aware of all of the problems that could be had. It is certainly very informative.
I will print out the info. & check both K/Bs against it.
Yes, we do get very high temperatures & humidity here. Over 40+ C in summer from December to March with up to 90% humidity.
This does not happen everyday, but in some years it can be very persistant.
The K/B does spend a lot of time in my van, & even though it is in a wooden roadcase, this would not be good for it having read the article as the van is often parked in the sun when I'm out & about.
The KN5 suffered the same fate when I was using it.
I will contact "WD Greenhill" & see how I go.