Not interference.

IIRC, my former service tech friend said this kind of problem is a defective drive IC.

You'll need to take it to a service station. But, call Sharp customer service and see if they will cover the repair.

Thanks for the info. I called Sharp customer service and they requested some digital photos showing the problem, which I did. They replied that they received them and will get back to me after technicians examine the pictures. All of my old CRT tvs lasted at least 10 years. Now this high tech $1300 set may require an expensive repair after only 13 months. Bad luck or reliabilty issue?

Probably bad luck. Sharp enjoys a decent reliability rating.

Did they hint at covering the repair?

I assume that Sharp customer service will want to identify the problem first before any discussion about repair costs. I will try very hard to get some help because it seems that the driver IC is quite expensive to replace.