according to meindl we get goretex liners because we want them aka gore's publicity machine tells us so.
it is always disaapointing when something fails, especially if has cost a few bob!
gary, meindl's boots - and i assume that there will always be manufacturing exceptions - are well made and very much fit for purpose. your foot in one boot will behave differently to when it is in another so it's nigh in impossible to even say that you never had this problem with x brand of boots.
take this experience as part of the learning curve that afflicts some more than others (it's certainly cost me a lot!). seek out and learn how to lace your boots differently to prevent/lessen foot movement and experiment with socks (the only good sock by the way is a sock that fits you properly - just like boots - irrespective of brand)
the lacing below will lock your heel at the back of your boot irrespective of how tight the rest is tied up - give it a try.