Back in 2016 a section of the front roof slid off the house!
There was another roof underneath so it was not a critical issue.
Meant to fix the roof in 2017 but didn't get around to it.
Zoom view shows where the shingles shifted and buckled.
The buckling didn't happen until later in 2018.
Took a picture of the back when all shingles were removed.

Unfortunately the plywood base was only 1/4 inch thick! Not up to code.
We opted to have new plywood installed over the whole roof.
Front of the house after shingles removed and new plywood installed.
Covering to protect roof from water and ice.
Finishing the back. Some items still on the front.
New roof looks great and is guaranteed for 50 years!