Based on what I read, the usb serial CDC connection uses usbser.sys as a driver on Windows. If you search for usbser.sys CDC on google, there are a lot of topic with people complaining about problems with this driver. It seems to be unreliable. For example: https://www.microchip.com/forums/m538194.aspx
And because reconnecting usb solves the connection, I think this driver is causing the problem.