I agree with you. I don't think there was a way to fix Lenny and Karyn's technical difficulty, except at the pit stop. If it would have made no difference, we would have just found out about it at the beginning of the next episode - where they got the time credit. Instead, we were told about the time credit about 40 minutes into the show.When Karyn got out of the car, she clearly knew they were not going to be eliminated. So we can conclude that, sometime during this leg of the race, the producers decided noone would be eliminated - and told Lenny/Karyn about it.
Good call on the editing at the end. I looked at it again and it appears that the part edited was: "It's one of THREE non-elimination points across this race." I think the producers knew there might be problems they couldn't fix so they left options open. When this part was filmed, they knew it was a non-elimination point - but did NOT know how many there would be thoughout the race.