Product review (1 stars): You need to improve the knob with epoxy
I had the same problem. Although I get free knobs from my local appliance store, this was not satisfactory. Knobs should not break in less than a year of normal use. Frigidaire's design, manufacture and quality control of their knobs is obviously flawed. That replacement knobs are sold to their customers, which will break again, is simple corporate arrogance.

So, you can do what Frigidaire will not do, improve their knob - by filling  the void around the knob stem with epoxy. When it cures you will have a solid trouble-free knob.

1. Gently pull a knob off a switch you do not use - e.g. the dryer signal  off-on switch.

2. Buy a tube of epoxy for plastic. I prefer Loctite Plastic Epoxy, but probably any good epoxy will work.

3. Put the knob in a vise or have another means to keep it from moving and level.

4. Mix up enough epoxy to fill the interior void around the white stem, that has the black metal sleeve in it.

5. Be sure you fill the knob interior up to the very top of the stem. (The first time I did this I did not fill with epoxy to the very top and the unsupported plastic broke after a while.)

6. Wait the required time for the epoxy to cure. After it cures, you have a improved, solid knob, which will perform for a long, long time. Problem solved.

Frigidaire should take note, but all they know is how to foist a flawed part onto the consumer to pay for again and again.

PS My 1 star relates to the short durability of the knob part.