The stinger has kind of taken over the industry even though it is not recomended. If you got carpet that is 20 years old its should be time to replace it.20 years ago they still made decent carpet
Some will get wrinkles easier than others. Pad type makes a big difference, room size and shape come into play and so does the walking areas.
If it was installed in the summer and it was hot, that might be a #1 reason that a kicker was successful.
A kicker rarely works so your installation is an exception.
Most carpets that I've restretched were done with a power stretcher, but using a stinger, not wall to wall stretcher tubes.