FTDI USB to Serial adapter disconnects on its own - after a while

I have an intermittent problem with a new USB-A to Serial DB-9 adapter with FTDI. If I leave it plugged in for a long time (for some unknown value of "long time") the device /dev/ttyUSB0 disappears, necessitating a reseating of the device in the plug. How can I keep the device from disappearing?

Code:$ dmesg | tail -n 9; echo; ls -lh /dev/ttyUSB0
[411973.086226] usb 3-1.4.4: new full-speed USB device number 114 using xhci_hcd
[411973.209077] usb 3-1.4.4: New USB device found, idVendor=0403, idProduct=6015, bcdDevice=10.00
[411973.209084] usb 3-1.4.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[411973.209087] usb 3-1.4.4: Product: Chipi-X
[411973.209089] usb 3-1.4.4: Manufacturer: FTDI
[411973.209091] usb 3-1.4.4: SerialNumber: xxxxxxxx
[411973.214147] ftdi_sio 3-1.4.4:1.0: FTDI USB Serial Device converter detected
[411973.214199] usb 3-1.4.4: Detected FT-X
[411973.225397] usb 3-1.4.4: FTDI USB Serial Device converter now attached to ttyUSB0

crw-rw----+ 1 root dialout 188, 0 Sep 2 15:50 /dev/ttyUSB0I can suspend/resume over a shorter time and /dev/ttyUSB0 stays around.

Also from dmesg output:

Code:. . .
[409673.987218] usb 3-1.4: clear tt 4 (9031) error -71
[409673.987457] usb 3-1.4: clear tt 4 (9031) error -71
[409673.987825] usb 3-1.4: clear tt 4 (9031) error -71
[409673.988215] usb 3-1.4: clear tt 4 (9031) error -71
[409673.988457] usb 3-1.4: clear tt 4 (9031) error -71
[409673.988829] usb 3-1.4: clear tt 4 (9031) error -71
[409673.989082] usb 3-1.4: clear tt 4 (9031) error -71
[409673.989389] usb 3-1.4: clear tt 4 (9031) error -71
[409673.989703] usb 3-1.4: clear tt 4 (9031) error -71
[409673.989877] usb 3-1.3: USB disconnect, device number 108
[409673.990250] usb 3-1.4: clear tt 4 (9031) error -71
[409673.990534] usb 3-1.4: clear tt 4 (9031) error -71
[409673.990835] usb 3-1.4: clear tt 4 (9031) error -71
[409673.991222] usb 3-1.4: clear tt 4 (9031) error -71
[409673.991453] usb 3-1.4: clear tt 4 (9031) error -71
[409673.991820] usb 3-1.4: clear tt 4 (9031) error -71
[409673.992073] usb 3-1.4: clear tt 4 (9031) error -71
[409673.992328] usb 3-1.4: clear tt 4 (9031) error -71
[409673.992580] usb 3-1.4: clear tt 4 (9031) error -71
[409673.992949] usb 3-1.4: clear tt 4 (9031) error -71
[409673.993203] usb 3-1.4: clear tt 4 (9031) error -71
[409673.993454] usb 3-1.4: clear tt 4 (9031) error -71
[409673.993824] usb 3-1.4: clear tt 4 (9031) error -71
[409673.994199] usb 3-1.4: clear tt 4 (9031) error -71
. . .Is the device defective?