Is there anything else that would cause this failure besides bad luck and a faulty or low quality chain? I just don't want to have to do this again for a third time. I know there are not many parts that contact or would stretch a chain and we already replaced most of them. Even if the part was aftermarket, it seems almost unbelievable to fail nearly immediately. Even the mechanic said he wouldn't of believed it if he wasn't looking right at it.
Thanks in advance
I'll tell you exactly what most likely happened because I do a great deal with engineering level failure analysis on chain systems for pulp/paper, mining and others. This is more common than most people realize and almost impossible to detect and predict at the user level.
Theres more than 1 failure mode and mechanism for a chain and sprocket failure so for the purpose of this comment- I assume it was the "right" combo for your application and the mechanic in question properly installed/tensioned/aligned it and your lubrication system was operating properly.
Here's what happens during chain and sprocket manufacturing.
Chains to NOT stretch- the pins and rollers wear thus "opening them up" giving the illusion of stretch.
These pins and rollers are made in machines literally by the millions at the time and frequently have batches that suffer during the heat treat section because of various things such as running speed, holdover, depleted oils, temperature problems and so forth.
There is very little legitimate QA/QC "over there" ( been there and seen it in person) so they get installed.
I have verified this many times in paper and mining with a Rockwell tester and tracing quality back through ISO systems on high dollar failures.
You can get a soft sprocket too but that's less likely.
Without doing the actual analysis, I can almost bet money that's what happened in your case. It has all the textbook ear marks.