I published the following D-Bus path in my grid meter Python script which fixes the oscillation in v3.42. A belgian P1 meter is only updated once a second.
# Used by hub4control to know how fast it can make its control loop.
# https://github.com/victronenergy/dbus-shelly/blob/master/meter.py#L91
# https://github.com/victronenergy/dbus-cgwacs/blob/master/software/src/ac_sensor_bridge.cpp#L113
service.add_path('/RefreshTime', 1000) # ms