Over the years, I've encountered several problems with brand new ICs where the companies have altered their datasheets as a result. In one case, company removed the IC from the market. One IC I used, I think the company revised the datasheet three times before I was done. If someone unfamiliar with the part used it today, they would have no idea that several modes that the hardware supports because they are no longer documented.
Were those modes terminally useless? Maybe someone could have used them for something?
In that particular case, I am using these undocumented modes for products we have in current production. The problem from the IC manufacture's perspective is they would have had to provide details about the cases I uncovered in their datasheet. While I would have thought errata sheets, I am guessing they just took the easy route and stripped the features all together. Maybe I shook their confidence.
From my experience, the story normally goes something like, I find a problem. Contact company. Company states I am an idiot and they can't replicate. I provide bad parts. Company eventually puts me in touch with higher level support who states they can't replicate. In the case of Analog Devices, I get a call one day from the designer of the part. Also get a call from their factory who provides me with details on how to screen for the problem. They correct the IC in the next product line and they also add changes to their factory testing of the ICs. It's always the same, time wasted dealing with the apps engineers, sales..... and finding the people who actually know what is going on.
In the case of previous part, I had found more than one problem. Once I worked the channels the first time, finding other root problems went smoother. They knew who I was and I had a bit more clout. Life of a designer.
Anymore, I don't do much with new parts so I dare say most of what I run into it the company take over, marketing/sales messing up the new datasheets.
I've moaned on this forum before about the 4000 series monostables we used at my old work in (luckily) just a couple of transmitter site remote controls, built "in house".
It's too long ago to remember the exact type number, but we used the devices to provide a quite long time delay, which was well within the range quoted in the data sheet.
We had to perform a modification which required messing with the wire wrap connections to the socket holding the device, so I carefully removed the IC & promptly lost it into the "black hole" which seems to surround workbenches.
No problem, plenty in the store!
Big problem!---- the time delay function didn't work properly with the new one!
Stealing a device from another part of the equipment, all was well, so the next trick was to check every device of that type number in the store, it was found that none of them worked in that circuit.
Digging through a ton of datasheets, we eventually found, on a loose, daggy looking errata sheet that some people had been having trouble achieving short delays with the devices, so the manufacturers modified the device to work well at such delays, buggering up its performance for long delays.
To "add insult to injury" they retained the original part number for the modified version & relabeled the original version with a new type number.
We just bought a bunch of the relabeled ones, changed our records/schematics & were "good to go" as we only had two of those remote control units in service, but imagine if someone had thousands of them in production or "out in the field!