In both the first two cases, the pilots knew about potential MCAS issues and discussed them with each other before take-off -- and they still had (terrifying) problems.
In those cases (if they are not two reports of the same incident), while MCAS was discussed prior to the flight, the actual incident appears to be autopilot related, and there is no mention of the trim running away and having to be disabled. In fact, the Captain's report mentions that he chose to engage the autopilot earlier than usual, "to remove the possible MCAS threat."
I'm a developer and not a pilot but I think that's pretty relevant. In both of those (two separate) cases, the pilots were aware of MCAS (it's not supposed to run when autopilot is on, right?) and tried to avoid any interference from it, yet they experienced interference anyway. One of those examples was nose down which sounds like MCAS and the other was unexpected leveling off at the wrong altitude.
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.
