Blade wobble on a power miter saw

Can you return the saw? It could be the blade, or the arbor/flange. Let them sort it out. You should either be able to get a new blade, or new saw maybe both. With that said, you should buy a nice blade for finish work and use the original for rough carpentry. Freud and many others will change the personality of the saw.

If it's not returnable, I'm sure you'll get the help you need here. Be specific in your question. Model number, blade size, tried rotating the blade...

I've had that happen to 2 different 10" miter saws. In both cases, there's a roller bearing around the blade arbor shaft. For whatever reason, one of the rollers in the bearing develops a flat spot along its length. When that happens to come around, it kicks the blade over, which means quite a lot at the rim.
One was a yard sale special, the owner said it cut funny. I bought the other (Delta) new and worked it to death. Great saw. So, off to see the repair dudes. $50 each and they cut like new.

if you have another blade, try it first. as mentioned the arbor flange and washer are the next things to try. if you have ever "jammed" the saw on a cut, that usually does it.

There is a good chance it is in the bearings or arbor. There is also a chance it could be in the blade, so try a different one. There could be a chance that you didn't mount the blade properly. Make sure the blade washers are seated properly and that the blade is not hung up on something. A small amount of dust or a wood chip could throw the blade off.

unplug saw. Mark a tooth, and rotate the blade, until the tooth is at max runout. Without rotating the blade or arbor, loosen blade and rotate 180 degrees. Check for runout again. If the runout is reversed, the blade is bent.

Or remove blade and check runout on the arbor flange. If ok, it's the blade, assuming there isn't anything on the arbor, causing the runout.

Check the backup collars the blade rides against.. Sometimes if the blade isn't tight enough it could spin enough to cause a burr either on the blade or the washer-collars which would create a problem...