dmesg:
[2052870.660000] hub 2-0:1.0: port 1 disabled by hub (EMI?), re-enabling...
[2052870.660000] usb 2-1: USB disconnect, address 64
[2052870.660000] ftdi_sio 2-1:1.0: device disconnected
[2052870.772000] usb 2-1: new full speed USB device using uhci_hcd and address 31
[2052870.972000] usb 2-1: configuration #1 chosen from 1 choice
[2052870.976000] ftdi_sio 2-1:1.0: FTDI USB Serial Device converter detected
[2052870.976000] drivers/usb/serial/ftdi_sio.c: Detected FT232BM
[2052870.976000] usb 2-1: FTDI USB Serial Device converter now attached to ttyUSB1
[2053284.052000] drivers/usb/serial/ftdi_sio.c: error from flowcontrol urb
[2053284.052000] drivers/usb/serial/ftdi_sio.c: update_mctrl Error from MODEM_CTRL urb: DTR LOW, RTS LOW
[2053284.056000] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0

/var/log/syslog
Oct 27 16:45:28 dora kernel: [2053284.052000] drivers/usb/serial/ftdi_sio.c: error from flowcontrol urb
Oct 27 16:45:28 dora kernel: [2053284.052000] drivers/usb/serial/ftdi_sio.c: update_mctrl Error from MODEM_CTRL urb: DTR LOW, RTS LOW
Oct 27 16:45:28 dora kernel: [2053284.056000] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0