One problem related to underbody shield has been reported for the 1997 Chevrolet Blazer. The most recently reported issues are listed below.
I just picked up my 1997 chevy Blazer oct 31, 2012 with 79000 miles on it. I noticed that there was a large amount of corrosion buildup on the under carriage of the vehicle. Luckily yesterday, while sitting in my driveway, I noticed brake fluid leaking behind the driver's side door. Under closer inspection, I found out that the rear brake line was severely corroded and had burst. Now I cannot drive my Blazer until I get this fixed. With this leak, I inspected the rest of my brake lines to which I've found both my front brake lines in a severely corroded state as well waiting to burst. This is a great safety issue.