Even metal can suffer from fatigue, but with plastics, what can be perfect today, can fail after a time. Sadly in some cases, only extended use will prove a problem. For example, polythene cold water storage tanks when originally introduced failed because plumbers carried on applying a linseed
-based sealant to pipe fittings. Glass reinforced plastics developed cracks due to being subjected to loads, which had not been taken into, account at the design stage. The vacuum pipes on Renaults are an example too. Failing either through vibration or chemical /
attack. (See 'juddering Meganes!')
As for the plastic bonnet catches loading, chemicals, lubricants, can all be factors coupled with inadequate design, not to mention faulty moulding techniques. The material is usually one of the engineering type plastics.
But the bottom line surely is the vehicle specification must be assessed for risk & safety in total. Then as with the cam belt be replaced at prescribed intervals. One would have thought the cheapest way for Renault would be to replace ALL the suspect catches. Good for public relations PLUS avoids damages actions, which invariably will escalate.
A point to watch though is to ensure that when taking part in any group legal action, that you insist in being kept informed as to the ongoing costs. Too often a group starts off full of commitment, the lawyers then get enthusiastic resulting in huge costs, which need to be borne in the long term - if the action is lost. This is especially important for the names on the claim sheet.