I’ll check to see what my model number is. I have 2 identicalI have a Ryobi 18v 12-inch chainsaw with a toolless chain adjustment. It worked great until the chain was well used and it stretched out. Then the toolless adjustment could not tighten the chain enough to keep it on the bar. I was very disappointed with it at that time. However, there is a simple fix to remove the stops on the toolless tightener which allows you to once again properly tighten the chain and prevent it from derailing. That one easy fix allowed me to continue to use an older, but still good, chain instead of having to buy a new one all the time. My rating on that Ryobi went from 3 stars before the fix to 5 stars once I implemented the fix.
Chains should not fall off bar track if your chain tightener is working properly.
If you have the same Ryobi chainsaw model I have, I can send you instructions on the easy fix. It really makes a world of difference.