many years ago in high school home ec we were taught to always tear our fabric length wise or the side with the selvedge that was to strighten it upI guess since being taught this that I do it I always tear my borders but about 1/2
inch wider than I want then I trim the fuzzy edges I don't know why yours got wavy on the end but I tear slow and have never had a problem 100 % cotton should tear very straight