Re “… increased frequency of severe weather conditions may be taking the probes beyond their original time of certification design limits.”
Also, consider any changes in the way in which we operate, the routes and altitudes now flown, and perhaps lighter weights in search of economy, all of which could place the aircraft in high risk areas. Add to that, the way in which humans react to bad weather – ‘not been a problem previously’ – ‘it will be OK this time’, 'can deviate too far - must save fuel'.
And especially where the ‘new’ technology radars provide an excellent picture – except the radar might not be able to show some of the hazards, or crews may not have been taught or be able to recall the hazards, i.e. high altitude ice.