Make sure you shake the bottle. If it is more potent of a smell towards the later half of the bottle I wonder if the concentration of the active ingredient has increased thus meaning the first half wasn’t fully dosing the tank. Just a thought.
I find that the secret is to disguise the smell with a splash of lemonade and a wedge of lime. It's quite a peculiar bouquet that's for sure! However, the mother in law never complains about it! Lol.
I have used Seachem Stability to successfully cycle 2 aquariums now, as well as to restore filter health after medicating or after very large water changes. This product has always worked well to establish or keep my bacterial filter strong and I will continue to keep a bottle on hand for situations in the future. I use it in conjunction with Seachem's Prime to turn ammonia into a form Stability's bacteria can use.