I saw that when it came out, but it was not on fixing bad ones, but the cost of runout damaging small expensive endmills.

If I were a production shop, I would only buy the sizes in current need for tool shanks that are specific sizes. And get high quality that has the sub tenths/microns runout.

But being a model shop guy, I buy the set's that are in my budget.

Most of which collect dust. At least that's the experience I have. I'm new to ER types, and have never seen this issue with the 5C and R8. But then I don't use micro diameter end mills either.

So the question is how to fix these damn cheap ER collets?

I did purchase a cheap 5C lathe collet chuck a few years ago with a D1-8 mount. That chuck had horrible runout, and I ended up buy a Bison brand to swap out on the lathe adapter. It had the exact same mounting holes and pilot, which was machined correctly. You would think with all the CNC machining that the quality would be near perfect for even the low cost tooling.