First, get some super glue.
Disassembled, your DD Stand should look like this:
Not everything in the above photo is completely disassembled but anyone who owns this stand should understand the instructions below. Make sure you keep track of where and how the screws, nuts, and washers go.
There are a total of 3 of these joint pieces included with the DD Stand. Do the following for all 3. Apply the super glue to the inner and outer rim. After you apply the super glue, LET IT DRY FOR 10+ MINUTES (or however long it takes for the glue to dry completely). You don't want anything touching the glue until it dries completely. While this may be super glue, when you're just letting it dry by air, it actually takes a lot longer to dry completely than you would think it should.
Once the glue is dry, you can reassemble the DD Stand.
The doll below is a Smart Doll customized with a Dollfie head. A Smart Doll can stand on her own two feet and has a telescopic stand joint attachment at the back if a stand is necessary. However, for this test, I didn't use the Smart Doll stand for the obvious reasons and I made sure she can't balance herself on her feet by putting her on her heels. This means the DD Stand needs to have strong enough joints to support the doll's weight.
The additional resistance provided by the dried super glue has dramatically improved the DD Stand's joint strength.
If you're buying a Volks brand doll stand, I highly recommend you buy one of the metal ones and avoid the plastic ones altogether. However, if you bought a plastic stand and regretted it, all is not lost. Use the super glue trick.