The key to beating any repeated reaction in this game is baiting.
If someone continually does anything, like spotdodge, this means that it has become a habit. Though you may be losing to it now, this is good news for you. You know that he spotdodges as a panic button, so, as you gain more momentum, he'll keep doing it, and you'll keep punishing it.
So, let's say you are tech chasing a Fox who keeps spotdodge shining you every time you are late on a tech chase. If you feel that you are going to be late, rather than going for it anyway and getting shined, dash in as if you are going for the grab, but then wait(or jab, jab is really good). This will bait out the spot dodge, and you can punish.
Punishing with what depends on percent. At lower percents, grab is usually good. At mid percents Stomp -> Knee. At higher percents, you can just Knee, or Stomp -> Knee, if you feel like it.
Spacies are hard, but Falcon can do it if his tech chases are seamless.