Mike–
The change is temporary in the beginning because you are setting new positions and may be using some muscles for the first time related to the new positioning. It takes a little time to unlearn a habit and establish a new habit/develop a new neuropathway for the change position. As you work with the position more you will see improvements with holding the changes.
You may experience it at night because you are completely relaxed.
It went away temporarily because the brace was a temporary fix for what was causing the issue.
Without addressing the cause the another symptom will come up.
Have you watched:
Pro Episode #11 Bench Set Up Q and A w/ Laura Phelps- Sweatt Pro User Request
Pressing Mechanics and The Knee Pushup Up Disaster/Froning and Bailey Edition
Banish Your Elbow Bench, Dip, Pull Up Pain, You Don’t Really Play Golf or Tennis Do You?
Burpee Smoked Elbows? Epicondylitis-ness? Voodoo it.
Better Benching and Pressing
Episode 81: Benching Global (Extension)