I agree with Roundball. Switching brands is not guarantee of quality control. If I had that slug, and others, I would call T/C, and then send them the slugs, and given them any information that might be on the box they came in that can identify the lot of the shipment. T/C would be able to tell you what to look for and where. I know T/C would do right by you, and probably send you a free box or two of new slugs, to replace the bad ones you had.
As to the complaint about being out of round, first measure the slugs to find out just How Out of round they are. Talk to T/C about that, too. I doubt that this is going to affect the accuracy of the slug all that much. However, if you absolutely need the same exact diameter of slug for shooting, get a sizing die and bullet sizer/lubricator--- you don't have to lubricate them, or make up a sizing die yourself, or at the local machine shop, and size your bullets. My brother has a sizing die for his pellets he uses in a high grade pellet pistol. It does make a difference in those light, small caliber, pellets and accuracy. In heavy caliber guns, the slugs can vary as much as 5 grains before they start hitting a different POI. Even home cast slugs need to be sorted by weight, and dimension for target grade accuracy. I have one friend who casts his own slugs, and then runs them through a swaging die and press to squeeze out the bubbles to get more uniform weight. Off a bench, you can see the difference in group size. Off-hand, there is no reason to bother, and he is a very good rifle shooter. Considering all the labor and effort it would take to deliver a slug that is consistent in both weight, and dimension, what you pay for those maxi-slugs is a good deal. They are sold for use in hunting, and not long range target shooting.
One last thought: The diameter of your bore is absolutely critical to good accuracy with slugs, of any kind. if you haven't measured the bore, do so. If the slug is more than .002" under bore diameter, consider using cigarette paper to paper patch the slug before loading it. Or use a card wad under the slug to seal the gases so they don't cut the sides and bottom edge of the slug.
I hope these ideas help you. I know how frustrating it can be when you find something you paid good money for doesn't work in your gun. :cursing: :thumbsup: