I can't comment on your grill specifically, but your first post said the difference was 50°F and one of your last posts stated it was 100°F off. Probably a bit of your frustration coming out. You have to keep in mind that this is NOT an authorized Traeger support forum. This is for Traeger enthusiasts to help one another. There is a ton of knowledge and help on this forum. But one thing no one can do is make someone change their mind.
What is acceptable to one, may not be for another. The advice given on here to adapt to the knowledge you have about your temperature settings is sound. But if you choose that you feel that is unacceptable, you need to look into a return or selling it privately. My Traeger is off in set temperature vs. pit temperature and for me I was fine with it once I learned what the actual temperature was at a given set point. Was I happy about it after shelling out a fistful of cash for my IW650, no. But for me, it wasn't a challenge that I couldn't work with or live with. Choices we all make for ourselves.
I also have a Yoder, which I got mainly because my IW650 wasn't big enough. Had I got the 885 I probably would only have the one Traeger grill. I also have a Kamado grill. The Yoder has its issues as well. If you think your Traeger burns through the pellets, be prepared for a consumption shock if you go to a Yoder. Also, pellet tunneling, the Yoder is way worse than the Traeger. Minor issues for me that I choose to accept. There is a cost difference between the two grills as well, previously mentioned by
@JPSBBQ. So comparing the two isn't on the same level.
You can adjust the ambient pit temperature on the Yoder. Yoder has a process you follow, then send them the date and username of the test and they will provide you with directions on setting an offset for the temperature. Traeger could probably offer an adjustment on the ambient pit probe, but that would open up all sorts of issues in user errors in adjustments.
You have to do what's right for you. Move on from the Traeger if it's nuances bother you.
I honestly believe you will get more help here from the users on this forum than you will over at the Yoder forum. To me, there doesn't seem to be any sense of community over there. Not a lot of activity, as no one seems to share cooks or discussions.
Anyone that does their research before making their purchase would see the common issues discussed about the Traeger. Can't trust a salesman to provide the facts, they get paid by selling things. If they told you that the thermometers on the Traeger were inaccurate, you'd have never purchased it. But had you come to this user/enthusiast forum you'd have read multiple posts about the issue.
I doubt you will resolve the temperature difference between the reading and actual, so you are left with two options.
Good luck with your decision.