If it's repeatably dead on at 25 and 50, it should be just fine at 100. If you had a scope problem that would throw you off paper at 100 then you would not be repeatably on target at 25 and 50 either. After all, a 15" paper is 7.5" middle to edge. If you're off by more than 7.5" 100, you should be off by 3.75" at 50 and 1.875" at 25.
Some scopes can't handle the shock of being fired in a stationary rest (Lead Sled). Get the gun on your shoulder and try it but, again, if it's a scope problem it should be noticeable at any distance.