Oscillating blades, they're expensive, it doesn't take them long to wear out.
When they're worn out, take your grinder and cut some new teeth on the blade. That's it. Then the blade will cut well again. As you see I made big triangle teeth. The little ones don't last long. There's not going to be a kerf on the new teeth blade. Either dont use it so much as a plunge cut, but more a side to side sawing while cutting with light pressure, or take some needle nose pliers and bend the teeth slightly in opposite directions to give it a kerf ike it had originally. I didn't kerf this wicked bladed I made and I will say it works as well or better than it did originally. In some ways much better. Cuts through shingles like butter.
I use this tool all the time in woodworking to correct little mistakes. Oscillating tools are not a replacement really for any other tool but once you realize the convenience and things you can do with them that you can't do easily with any other power tool, the oscillating tool becomes an indispensable addition to your tools. At least it has to mine.