It is a shame, but many boats suffer from cracks in the transom. They can vary from superficial to places where water intrusion can occur. If water intrusion occurs, the plywood can rot and ruin the transom.
You want to watch for this condition and attempt to seal the crack as soon as you can. If it can be sealed and does not get worse, you should be okay. If it begins to cause rot, there is a product named "Git Rot" which can be injected to solidify the wood in the area. I believe it is just thin epoxy capable of saturating the wood and waterproofing it.
Her is a link you might want to look at:
BoatLIFE | How to use "Git"-Rot