Old drills randomly starts slow and rattling (if at all)
JJM your understanding of how motor brushes work is lacking some practical experience.  For less than 20$ you can probably have both running like new and gain the experience.
Holding the motor at an angle may cause speed changes. Bumping the motor can get them going or kill them.
I looked for AGE brushes and a video came up , easy to change , 2 screws remove the black grip and the brushes are right there.
Some brushes when the wear through damage the armature. Pulling the brushes is usually not difficult and on some models down right simple so please check them or they will be yet another thing for the trash.
Some skill motors
Removing a plastic disk that is screwed in and pulling the brush takes a few seconds other models opening the case and pulling the brush may take a few minutes. Most brush sets can be found for under 12$ and some for as little as 2.50$ for a pair.
I would encourage you to at least try before the armature is damaged and you might find the motor preforms like it should. And you learn a new skill that is rapidly being lost.