5.40 --> 5.41 BLE regression for me

This is surely my own fault. But my understanding of dbus is quaint enough that I don’t get what the problem is. I use a python3 variant/evolution of the example-advertisement and example-gatt-server to make my Linux SBC a BLE peripheral. Upgrading my bluez libraries from 5.40 to 5.41, I’m suddenly getting an error that I wasn’t seeing before:

ERROR:dbus.connection:Unable to set arguments (dbus.ObjectPath('/'), {}) according to signature None: <class 'ValueError'>: Unable to guess signature from an empty dict
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 604, in msg_reply_handler
    reply_handler(*message.get_args_list(**get_args_opts))
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 401, in _introspect_reply_handler
    self._introspect_execute_queue()
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 387, in _introspect_execute_queue
    proxy_method(*args, **keywords)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 137, in __call__
    **keywords)
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 584, in call_async
    message.append(signature=signature, *args)
ValueError: Unable to guess signature from an empty dict
ERROR:dbus.connection:Unable to set arguments (dbus.ObjectPath('/nelson_irrigation/twig_pilot'), {}) according to signature None: <class 'ValueError'>: Unable to guess signature from an empty dict
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 604, in msg_reply_handler
    reply_handler(*message.get_args_list(**get_args_opts))
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 401, in _introspect_reply_handler
    self._introspect_execute_queue()
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 387, in _introspect_execute_queue
    proxy_method(*args, **keywords)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 137, in __call__
    **keywords)
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 584, in call_async
    message.append(signature=signature, *args)
ValueError: Unable to guess signature from an empty dict

One of the errors (the second) goes away if I just try to bring up advertising (no application/services defined).

The only thing I can see that I am doing significantly different from the original examples, is that I derive my PATH_BASE as ‘/nelson_irrigation/twig_pilot’ rather than '/org/bluez/example/service’. I notice that the PATH_BASE value is showing up in there. Does this PATH_BASE matter more than it used to (it was basically arbitrary before)? If so, what do I need to change to make it work again?

TIA