Problems accessing ESP from Windows 10 WSL

[apuder]

In the past I was able to access the ESP from WSL. I haven't done it in a while but now I'm having issues flashing. I'm using Window 10 pro, version 1809, OS build 17763.253. I have Silicon Labs CP210x USB to UART Bridge installed (driver version 10.1.4.2290). Windows reports the device to be working on COM11. I have an ESP32 connected and I can use putty to connect to it via COM11. However, I cannot access it from WSL:

ls -l /dev/ttyS11
crw-rw-rw- 1 root dialout 4, 75 Jan 21 09:57 /dev/ttyS11

python
Python 2.7.12 (default, Nov 12 2018, 14:36:49)
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import serial
>>> ser = serial.Serial('/dev/ttyS11')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/dist-packages/serial/serialutil.py", line 180, in __init__
self.open()
File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 294, in open
raise SerialException(msg.errno, "could not open port %s: %s" % (self._port, msg))
serial.serialutil.SerialException: [Errno 5] could not open port /dev/ttyS11: [Errno 5] Input/output error: '/dev/ttyS11'

Any suggestions?