The twig girdler may be at fault.  This is a beetle which makes a cut into the tree branch and deposits an egg, causing the end of the branch to die and fall.  A primary indication of this pest is that the twig looks cleanly cut from the branch.  This looks to be the case with your twigs.  Twig girdlers do not cause major damage to the tree; they just cause a bit of a mess for you to clean up.

For more information about  this pest, see https://hortnews.extension.iastate.edu/2007/10-8/TwigGirdler.html

Thank you for the response. I researched twig girdler earlier and saw that they leave a hole in the twig where the larvae bores into. However, there are absolutely no holes in my oak twigs. Everyone I've seen is solid,

I asked other people who serve as experts on the Ask Extension panel to chime in with their views as to what is causing your twig drop.  One thought it was squirrels,  while another thought not.  Here is a great response that includes some links:

The following publications address the question, but maybe not in a definitive way:https://bygl.osu.edu/index.php/node/1882https://mdc.mo.gov/trees-plants/tree-care/established-tree-care/tree-branch-flagging
I don’t think the cuts look like those made by squirrels.
Although periodic cicadas don’t occur in Minnesota, annual cicadas do. I believe they also damage tree twigs but apparently not in significant numbers. The OSU publication shows twig drop reaction to cicada damage (detachment at the stem nodes) that looks somewhat like what we see in the photos Karen Fine submitted:

We might need an entomologist to confirm or rule out the possibility that an unusual local number of annual cicadas could account for the twig drop in this case.

Have you seen a large number of cicadas in your area?  If so, this may be the cause of your twig drop.  Otherwise, as you can see, I'm sorry that we don't have a definitive answer for you.  

Again, I really appreciate your attempt to solve this mystery! Negative on the cicadas. This happened to just one white oak tree out of several trees on my property. Another person thought it was due to the drought and the tree is trying to store moisture before going dormant. But I simply can't imagine how a tree can just pop off a twig at the knuckle like that...Oh well. We tried and I thank you and your organization for the effort!

Karen Fine

If we can find a better answer, we'll let you know.  I'm  glad it's only one tree, and it sounds as though, whatever the cause, it won't really harm your tree.