We don't know when or how LE challenged Barry during his 3 30 hours.... but I can imagine this:
LE: Barry, walk us through Saturday.....
BM: Listen, I got up early. Picked up MG, we raked the beach area. Came home for lunch, veggie soup. Went back to town to get hot tub supplies and do a mechanical thing on the Bobcat, was there allllll afternoon. Went back home about 4.... and had more soup with Suzanne. We had soup until bedtime.... got up early, left her asleep at 5....
LE: hmmm. Your vehicle data and surveillance video would say otherwise, that you WEREN'T doing a mechanical thing to your Bobcat for 5 hours.
BM to LS: just because I forgot the time I was doing a mechanical thing to the Bobcat....
Remember he wasn't in his right mind when LE was questioning him, having just learned that his wife was missing.
Or... to the point, Barry wasn't in anyone's right mind WHILE getting his Bobcat repaired precisely because it happened in the sliver of time between surveilling his backyard and murdering his wife.
Anyway, IMO this might be how that mechanical thingy and timing came into play, if he tried to use the repair to alibi himself for Saturday, depending on what LE showed him.
‘People don’t know the truth’: Suzanne Morphew’s husband breaks silence after three months | FOX21 News Colorado