USRP UHD Source problem

[Mike Markowski]

I'm running gnuradio companion 3.8.1.0 (Python 3.8.6) on Ubuntu 2020.10. 
 After a few weeks away from gnuradio, today I get errors with the USRP 
UHD Source, and previously working flowgraphs no longer build. 
(Previously built flowgraph python files still run fine.)  The attached 
flowgraph doesn't get much simpler, but building yields:

Generating: '/home/mm/sdr/fm/uhdTest.py'
Generate Error: (NameError("'len_tag_name' is not defined"), 
'uhd.usrp_source(\n    ",".join((${dev_addr}, ${dev_args})),\n 
uhd.stream_args(\n        cpu_format="${type}",\n

[... on and on ...]

, uhd.ALL_MBOARDS)\n% else:\n# No synchronization enforced.\n% endif\n')
>>> Failure
Traceback (most recent call last):
  File "memory:0x7f3082ab36d0", line 136, in render_body
  File "/usr/lib/python3/dist-packages/mako/runtime.py", line 106, in 
__getitem__
    return compat_builtins.__dict__[key]
KeyError: 'len_tag_name'

[... still more...]

Is anyone else seeing this error?

Thanks,
Mike

uhdTest.grc
Description: application/gnuradio-grc