Earlier quoted context omitted.
Self-consistency and consistency with your lived experience are good heuristics. Reality is self-consistent, so anything that doesn't add up indicated an error in the source or your understanding of it (or both). EDIT: I think it's a kind thing you need to tune yourself into. OTOH, I've observed many (most?) people seemingly being completely oblivious to self-consistency issues of their beliefs and mental models, or…
Reality is most likely self-consistent, but as we can only experience a tiny part of it it‘s impossible to tell. Also, parts of reality may appear to be contradictory with each other when some pieces are not known.
Exactly. This tells you where something is off. The problem may be your lack of understanding or wrong understanding, or it may be with the source, or the framing, or you may have hit a genuine lack of data - still, the puzzles don't fit in some area.
And yes, not all self-consistent understanding is correct. But all inconsistent understanding is incorrect. And the more knowledge you gain, the less likely it is that it'll all connect self-consistently, but still be very wrong.