Oh I saw this coming after reading your first paragraph! Awesome idea, I'll add it as a #4, although I feel as though this idea doesn't exclude it being a time travel, or alternate universe Harry.
Maybe I worded that part poorly. I actually agree this explanation makes it more likely it was time travel. Look at the car explanation:
Harry's car is stolen. Someone in the future warns Harry so he moves the car and it isn't stolen. The problem is the new future, the car isn't stolen, so Harry isn't warned, which means he doesn't move the car, which means it is stolen, which means he is warned, which means.... and it repeats forever.
This is the same problem that applies to LC. If LC blows up, causing someone to go back in time to fix LC, then LC doesn't blow up in the new future and nobody will go back in time, etc...
Now look at this chain of events:
1. Harry's car is stolen
2. An earthquake causes the parking garage where Harry's car is parked to collapse.
3. Future Harry wants to save his car from the Earthquake and goes back in time and moves it.
4. In the new future, Harry's car isn't stolen, but the Earthquake still happens. Thus, Harry still knows he needs to move the car and as a side effect, he gets to prevent his car from being stolen without creating a paradox.
Applying that to LC we get the same result.
1. LC blows up
2. Some other chain of events create a situation where someone needs to use LC and doesn't have enough time to build one.
3. A person goes back in time to use LC, which requires them to first fix the glitch.
4. In the new future, LC no longer blows up, but as long as the series of events in #2 still occur, then the time traveler still learns of the need to travel and gets to fix LC without creating the paradox.