Astromechanics returns no data intermittently

[Physarah]

I 06-29 08:21:43.956 Moving ZWO Filter Wheel (1) [Camera: 192.168.80.204] to position 2 (luminance)
I 06-29 08:21:45.711 Taking dark frame before autofocus on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1.
W 06-29 08:21:45.716 No focus offset found for blank filter.
I 06-29 08:21:45.721 Moving ZWO Filter Wheel (1) [Camera: 192.168.80.204] to position 1 (blank)
I 06-29 08:21:59.230 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 0, 'total_positions': 11}
I 06-29 08:22:24.276 Moving ZWO Filter Wheel (1) [Camera: 192.168.80.204] to position 2 (luminance)
I 06-29 08:22:32.434 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 1, 'total_positions': 11}
I 06-29 08:23:03.884 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 2, 'total_positions': 11}
I 06-29 08:23:35.329 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 3, 'total_positions': 11}
I 06-29 08:24:06.772 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 4, 'total_positions': 11}
I 06-29 08:24:38.223 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 5, 'total_positions': 11}
I 06-29 08:25:09.716 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 6, 'total_positions': 11}
E 06-29 08:25:09.929 _thread.ExceptHookArgs(exc_type=<class 'serial.serialutil.SerialException'>, exc_value=SerialException('device reports readiness to read but returned no data (device disconnected or multiple access on port?)'), exc_traceback=<traceback object at 0x7f6a797900>, thread=<Thread(Thread-190, started daemon 547264389600)>)
I 06-29 08:40:54.723 Moving filterwheel to r_band for autofocusing on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1.
E 06-29 08:40:54.731 Unable to apply focus position offset on ZWO Filter Wheel (1) [Camera: 192.168.80.204]: error(5, 'Input/output error')
I 06-29 08:40:54.735 Moving ZWO Filter Wheel (1) [Camera: 192.168.80.204] to position 4 (r_band)
I 06-29 08:40:57.289 Taking dark frame before autofocus on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1.
W 06-29 08:40:57.294 No focus offset found for blank filter.
I 06-29 08:40:57.298 Moving ZWO Filter Wheel (1) [Camera: 192.168.80.204] to position 1 (blank)
I 06-29 08:41:08.162 Autofocus status on Astromechanics Focuser (XXXXXX) on /dev/ttyUSB1: {'is_finished': False, 'completed_positions': 0, 'total_positions': 11}
E 06-29 08:41:08.165 _thread.ExceptHookArgs(exc_type=<class 'termios.error'>, exc_value=error(5, 'Input/output error'), exc_traceback=<traceback object at 0x7f8f32d7c0>, thread=<Thread(Thread-205, started daemon 547264389600)>)