I removed all X10 devices from alexa list, as suggested by Mr.T., Alexa rediscovered the devices and am back in business,
During the the process, I discovered that some of the devices were not being discovered by Alexa even after couple of discovery cycles. I found that by updating the bridge and reinitializing the bridge couple of times, all devices were discovered. During the repeated discoveries, few devices were rediscovered and again as suggested by Mr. T, I deleted the duplicates.
How long it will work, we'll see.