Can a Xfinity damage a Cable Modem with their equipment when testing line

Can a Xfinity tech damage a cable modem when they are testing the line?   I recently had a tech come to my house because at times my internet service drops periodically during the day (expericed with old modem and had not tested with new modem, new modem was working for a day before tech came).   During his testing my new cable modem stopped working all together (all lights blinking).   Is it possible with their equipment that they use to cause my modem to stop working?