I found a great discussion on applianceblogs.com on the exact issue, which was igniters failing because of deflector plates being too close and melting onto the igniters. Applianceblogs.com directed me to AppliancePros.com, which had both the NEW deflector (with 4 inch cut to prevent melting) and igniter. Replacing the deflector was straightforward, but required some effort since the screw holes were different sizes. Had to roll out the oven (pretty easy) to fish new igniter around and re-connect. Oven is working fine now, thanks to the blog and AppliancePros.com, although the site needs to be updated since the parts work for my CGS990SET4SS.