Funny story some years back I bought a brand new bike (I have been peddling to work as much as I can the last 25 years). Real leap cost wise as we were pretty broke, but the old one had fallen apart, I had to ride a bus or bike so we bit the bullet as only one auto. Nothing fancy but a good mid level mountain bike.

The 3rd day things got weird on the crank, hmmm, nut came loose. Ok, down to the bike shop, I guess I should have been suspicious as they had a hair dressing op on one side, 3 foot wall and the bike shop on the other. Only in Alaska. I had the tools but it was, this is weird, never had a crank assembly nut come loose.

Watching him he did not realize it was a revers thread, hmmm, this is not good, very studiously ignored me as I tried to coach him.

Next time it took 2 days to loose up, I tightened it myself and then loose again, back to shop.

I think the 3rd of 4th trip he looks at me and says "You peddle bike wrong!" Really? Can you show me the right way?

At that point it was, give me a new bike or my money back. He gave me my money back (wrote a check and I went down to their bank and cashed it!)

To this day I wondered what in the hell you could screw up on a bike crank nut or the assembly that would cause it to loosen up. Something pretty strange.