There is no evidence, in these reports, that 'interference' from MCAS had anything to do with it. The fact that the problem occurred when the autopilot was engaged (and MCAS, therefore, supposedly disabled) and was resolved by disengaging the autopilot, suggests a problem with the autopilot, not MCAS. The captain's report speculates about possible causes, but MCAS failure is not on the list, even though, as we know, the captain was aware of MCAS and its failure modes.
From the reports:
Synopsis
B737MAX Captain reported an autopilot anomaly in which led to an undesired brief nose down situation.
Synopsis
B737 MAX First Officer reported that the aircraft pitched nose down after engaging autopilot on departure. Autopilot was disconnected and flight continued to destination.