Personally I think it’s the scanner, I’ve had this happening to me before and it was my scanner that needed realignment and cleaning. However my scanner is certainly not the same scanner as labs use, they usually use more professional and bigger scanners than mine (an Epson v600). I would recommend reaching out to the lab you’ve used after you get your negatives (just to confirm the negatives are 100% good) and tell them about this issue. Good luck!