Interpreting your question more broadly along the lines of "would I be non-compliant with the ADS-B Out Rule":
RTCA's DO-260, the standard that defines requirements for 1090ES ADS-B Out and In systems, states the following in section 184.108.40.206.2.12:
The ADS-B Transmitting Subsystem shall terminate broadcast transmissions of the Airborne Position Message when position (latitude/longitude) and altitude data are not available for a period of 60 seconds.
Note: For the Airborne Position Message, altitude data alone is sufficient
to maintain broadcast of the Message once the Message has been
initiated. When only altitude data is available, the Airborne Position
Message continues to be transmitted even after 60 seconds. However, if
the altitude data is not available for 60 seconds, then the Airborne
Position Message transmission is terminated and the conditions for
start-up defined in §220.127.116.11.2.1.2 are necessary to resume the
transmission of Airborne Position Message.
Similarly, for the velocity messages:
The ADS-B Transmitting Subsystem shall terminate broadcast
transmissions of the Airborne Velocity Message if input data necessary
to update the subfields of the Airborne Velocity Message [...] is not available for a period of 2.6 seconds.
Interestingly, however, there are additional messages (e.g. status messages, identification messages, etc.) that will continue to be broadcast even in the absence of usable position information:
The ADS-B Transmitting Subsystem shall not terminate broadcast
transmissions of Aircraft Identification and Category Message even if
input data necessary to update the Message is not available.
Comparing this against the text of the ADS-B Out rule, §91.225:
§ 91.225 [...]
(b) After January 1, 2020, and unless otherwise authorized by ATC, no
person may operate an aircraft below 18,000 feet MSL and in airspace
described in paragraph (d) of this section unless the aircraft has
equipment installed that
(1) Meets the performance requirements in [...] TSO-C166b [...]
(2) Meets the requirements of § 91.227.
(f) Each person operating an aircraft equipped with ADS-B Out must
operate this equipment in the transmit mode at all times [...]
So, one could say that you have a properly certified ADS-B transmitter installed, you are operating it in transmit mode, and it is actually broadcasting messages; therefore you are in compliance with the rule.
That said, I am not sure I would risk my CFI ticket on this argument...