On my first cruise, I used generic Bonine. I've used Bonine all my life to combat (pretty serious) motion sickness. I really didn't feel great and I had a lot of vertigo.
Then the next time I traveled (not a cruise) I realized that generic Bonine wasn't working for my air travel either and I chucked it and got brand name Bonine. I haven't had any issues since. I've actually experienced this before. When I was pregnant, I had very serious nausea and vomiting (like, we had to go to the ER and I had to have two bags of fluids serious). I was on a prescription medication for my entire pregnancy for this condition. Once, when I got a refill, the pills were slightly different - a different manufacturer and they didn't work! I went back to the pharmacy and they got me the other brand and they worked. The pharmacist said that this wasn't completely uncommon. Sometimes generic medication formulations can vary slightly.
Anyway, I always buy brand name Bonine.
For our second cruise (before I realized the Bonine situation) I did buy a patch and I used it for three days, changed it out and then after the fourth day, I started having a lot of trouble focusing on things close up. I was having a hard time reading my book or menus. I was squinting and holding it far away from me - the whole nine (and no, it wasn't on my fingers, I made sure to be extremely careful of touching my eyes after application). Our final day was in CC and I realized when we got back on board, my patch had fallen off. I didn't put another one on, but I was fine.
Since then, we did Alaska and I used Bonine all week and was fine (but we had a really smooth cruise, so who knows). We have another one coming up and I'll take my patches, but they are a last resort.