Based on discussions on forums, under bonnet insulation pads drooping as a result of shrinkage seems to be quite a common problem.
VW seem to adopt their usual inconsistent approach to replacing these under warranty - some are replaced without question whereas others aren’t; where VW have declined warranty claims they seem to do so on the basis of the shrinkage being due to an ‘external influence’ - either heat shrinkage as a result of heat generated by the engine / turbo or by water through improper washing of the car
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The majority of the replacements also shrink, so presumably VW’s supplier haven’t changed the materials used in the manufacture of this part.