CADET TRAINING- Star Trek the Animated Series - "Yesteryear" review/discussion

We continue our Cadet Training with Star Trek The Animated Series season one, episode two - "YESTERYEAR".  After a trip back in time, through The Guardian of Forever, Spock returns and discovers that he's been erased. Written by D.C. Fontana and first aired on September 15, 1973. This is the second time that we see The Guardian of Forever, or Carl, as we learn on Discovery. How does time get  "broken" and "fixed", could we see something like this happen on Picard season two? Let's see what's out there.