Steps to find the glitch:
Step 1 - Enter a Barracks, Factory, Hero Command, Starship Command, or Cantina.
Step 2 - Select the "I" icon attached to an elite unit.
Step 3 - Use the side arrows to navigate to a regular troop that you have unlocked.
You will see that there is the option to upgrade the unit if you have the necessary resources, even if your Research Lab is not of the proper level.
If your Research Lab level is inadequate, the upgrade take the required amount of resources and start the upgrade.
You will then be notified of an error, and you will have to reload the game.
When the game loads, the upgrade will have stopped, and all of your resources that were used in the failed upgrade will be returned.
This glitch has happened to many people, including me.