I am not sure why it passed the left turn in your first video, but from your updated videos, it definitely looks like it is finding a false finish.
The Zumo maze solving program works by following the line until it senses a turn or intersection. Then, it reads the line sensors, moves the Zumo forward a little bit, and reads the sensors again to compare the readings. Comparing the readings determines whether the line continues forward and also if the endpoint is found. To me, it looks like your robot is not quite moving far enough forward to clear the line before taking the new readings.
The distance it moves before taking a new reading is determined by the
INCHES_TO_ZUNITS parameters. The
INCHES_TO_ZUNITS parameter was determined experimentally and found using 75:1 HP motors with partially drained batteries, so it could be too low if you are using a different gear ratio or your batteries are too drained. I would recommend trying again with fresh or fully-charged batteries first, and then if that doesn’t work, could you try setting the
line_thickness back to 0.75 and see if you get any better results? (You could also try increasing the
INCHES_TO_ZUNITS value instead, but I suggest trying the default values first.)