I've bought btms that had a fishy smell right out the bag. The manufacturer stated the smell varied from batch to batch and the manufacturer, but that there was nothing wrong with it.
I used it the same as always. The smell went away once it was heated. I had no problems with any of the products created with it.
I've never overheated it as it's usually gently heated with the other oil soluble ingredients. I've also used it in a one pot emulsion with no problems. I don't make so called lotion bars so idk how melting it in the oven helps that sort of thing. My beakers are too large for microwave. I've got stainless pitcher or heavy bottom sauce pan for heating. Years & gallons of products later and it always melts. I wonder if she mixed up her ingredients.