After using the microwave for a month, the amount of time to heat has increased significantly. For example, 1 cup water now takes 3 minutes to reach 158 deg and 4 min-40 sec to reach boiling (212 deg)
This model KEMS308SSS02 was installed in July 2008 in a new condo. It was never used until Feb. 2011 when we moved in as the first owners.
Any advice would be appreciated.

Have had this oven for 8 years. At least three times, usually after using the clean cycle in the main oven, the latch mechanism has broke and the oven door will not open. In March they installed a 'new design' to prevent this. It's seven months later, and it broke again. Has anyone had similar experiences? How did you resolve?