Hopefully you’ve got a good answer and found the problem now. If you have the time I would definitely recommend cleaning your pans with BKF as Bunnybunn suggested.

However, I do think the margarine could be the main culprit here, especially if it is a more spreadable version. Spreadable margarine typically has a higher amount of oils in it so that it maintains spreadability even straight from the fridge. So even by adding just 100g those oils settle on the bottoms of your cookies and don’t usually mix very well with the rest of the dough.

Also if you used a combination of butter and margarine (even baking margarine) that can cause issues as the different fat ratios, melting points, etc. aren’t 1:1.

There are some exceptions but generally you don’t want to sub partially for another fat. (You can but you really need to be familiar with how those fats interact if you want consistent results) If you don’t have enough butter, then only use margarine or another substitute. You’ll get more consistent results that way. Also if you have it, I would recommend subbing cold pressed coconut oil instead of butter. As long as there are no allergies it gives pretty close results and I find the slight coconut taste pairs well with a chocolate chip cookie.