1/8" sounds like a lot, but some saws cut in a rocking motion, so at any point in the blade's travel, up & down, it may not be perfectly 90 degrees, front to back. You may be able to turn the motor of your saw, with a screwdriver (look for a slot in the end of the motor). If so, you can check for vertical cutting motion by taking a 2" machinist's square, place it against the blade and turn the motor manually. Watch carefully as the blade moves up & down to see if it exhibits a rocking motion during the up & down travel.
You can also check this with a thick piece of wood, 1 1/2" to 2" thick, depending on your saw's capacity. Make sure it has a square edge. Turn the saw on and gently push the edge of the wood into the blade. Don't push hard, just enough to make a slight kerf on the edge. You should be able to tell if the blade is cutting to the same depth, top & bottom, by examining the kerf.