i don't know, i feel like once when i had dosed i had that issue, but not really a recurring issue. and i guess because i have not tried vodka dosing, and have only stuck with biofuel and MB7 since near the start of my tank, i have to say it's working. is it the best bacteria/carbon combo i can use? i have no clue cuz i have nothing to gauge it against or compare it to. but with the insane amount of corals i have packed into my 30 breeder, i will say it's done it's job in keeping water clarity to a maximum, nitrate down, and good health and color to everything. algae was a problem but that is usually expected during the first few months of a tank. now though, i have been lucky to have very minimal algae growth.
sorry i went off topic, but yes i do feel like i was bugged out once or twice from some kind of mucus-ey stuff that came out of the bottle when i dosed a while back. i'm guessing trying to shake the bottle up right before using it may help a little bit, and also make sure the bottle was fresh and not opened or exposed to a lot of air before you used it.