Took my car out of the garage yesterday evening after about 3 weeks and noticed the top of my head was touching the headliner. Initial thought was that the seat was somehow in the wrong setting. A quick visual inspection revealed that the headliner was sagging a lot. My car is a 2018 Cayman. Put into service in April 2018. I believe it was a Nov 2017 build and has about 15000 miles. The car is garaged so does not spend all its time in the Florida sun. The garage is not airconditioned but it is definitely cooler than outside.
Am bit disappointed that it only took three years of service to get a headliner sag. I have had this happen in my BMWs but that has taken many more years than this. A word of caution for you for the future to watch out for your 982s. I searched the forum and couldn't find many of these but i see that is normal in the 981s.
Will take to the local dealer for the warranty fix.