1. Buy a good replacement nipple like this one from Cabela's.
The Bobcat nipple might be threaded too close to the bottom of the drum. This interferes with getting a strong enough flame to reach the powder through the narrow flame channel.
So a better nipple should throw more flame.
2. Use the smaller fffg or P powder granulation so the powder can travel down into the flash channel & drum easier and closer to the ignition flame.
3. Clean out the flash channel, drum and nipple as much as possible after each shooting session. It can be tricky if you don't use the pump & flush water method of cleaning, and even then you still need to stick something in there to clean out any build up of residue which narrows the channel.
I use solvents and twist a cotton swab in one direction only to not have the cotton tip get pulled or broken off. A small nylon flash channel brush, doubled over pipe cleaner (they're tough to use too if any material falls off), or a thin wire like object used with a twisting motion to get down to the bottom of the channel through the cleanout screw opening and to scrap the sides.
Soak the nipple and use a nipple pick or needle to clean it out, and look to see daylight through it afterward.
4. I've never heard of Bobcat ignition problems persisting after buying a better nipple. But if the problem did continue, I would consider drilling out the bottom of the old nipple and possibly shortening the nipple fractionally to create more room at the bottom of the drum for the ignition flame to travel.
A nipple with a long stem can be shimmed upward very slightly to have a similar effect, but you need to be careful that the nipple has enough threading to not blow out, especially with students shooting it.
That's why simply drilling out the bottom of the nipple out might be another option to try if the ignition doesn't improve with a better nipple.
5. BTW, you might be able to buy a musket cap or 209 primer nipple to fit the Bobcat, but using those primers can be more expensive too.