Can There Be A Batch Of Zoloft?

I’ve taken the brand name 50 mg Zoloft for 13 years but sometimes I’ll get a refill prescription that doesn’t seem to work. But then with another prescription it seems to kick in. They are both brand name so I can’t imagine anything being different. But I can’t help but think they are somehow different but I think it would only make me sound crazier to ask the manufacturer. I’m sure the psychiatrist would just want to raise my dose but I’m sort of resistant to that.
maybe someone else has experienced what i have.

That does not happen

i have never beard of this and dont think this would sver happen one in a million chance wvery other batch you get is different