Threads like this remind me of my concerns and discussions with different folks at S&W in the early & mid 2000's, when I was wondering about the ILS and reading some negative stuff in magazines and online.
When I attended a revolver armorer class in the mid 2000's, I asked different armorers in the class whether they had experienced any ILS problems, or had any reported to them by people at their agencies. Zip, nada, none.
I asked some different armorer instructors over time about it, one of whom was a frequent revolver shooter in competition. Again, no problems experienced or seen.
The Repair guys to whom I sometimes spoke said that while they'd received revolvers for warranty claims involving 'the lock', the actual problems requiring correction didn't involve the lock. Other production issues were said to have been involved, like stubbing involving the DA hammer sear.
One of the longtime LE customer contacts (point of contact for guns being returned for warranty issues, both for LE and regular customers) told me that he remembered the ILS spring had been revised while development work was being done on the X-frame, (.500 S&W MAG), so the heavy recoil didn't over power the spring. Well, I did see that the torque lock spring was listed in the Parts List as a revised part back in '05, but they revise parts all the time.
I saw a fair number of .38SPL +P and .357MAG J's come through our range, from Demo guns, to LE off-duty/Secondary guns and a number of privately-owned (CCW, not LE owners). Never saw or heard of a ILS-problem with any of them.
Now, being familiar with the way the ILS locking arm & its spring are installed, including the way the itty bitty spring had to be installed in the locking arm (forcing one end of the spring past a small detent nub in a slot in the locking arm), and the way the little assembly is installed so the free (other) end of the spring has to be positioned and secured in its recess in the bolt channel, I could see how an assembly or installation problem might be possible if someone wasn't attentive. One guy at the factory had mentioned that there had been some concern about assembly/production attention to the ILS in the early years.
Personally, I rather suspect if the ILS (aka- the lock) were a problem for the past 25 years, there would easily be examples of it having been proven to be problematic being paraded around.
Not liking the way the assembly adds another 5 parts to a revolver, or the aesthetic appearance of the ILS, are different things than actually having the design and functioning being a problem.
I've actually met and spoke with some owners who liked being able to lock and disable their guns since they had kids in the house. Go figure. (That's why I bought a couple safes and a couple lock boxes, myself.

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