frontier...Sounds like you have a touch hole problem, not a lock problem...
If you are getting flashes in the pan and/or delayed ignition, your touch hole is too small, not coned or not located in the proper location, when you close the frizzen, the touch hole should be behind the heel of the frizzen...
In other words, high, above the pan, but centered...

Everything looks fine but you can never tell unless you play with it. After hunting season i plan on deepening the pan a little and see how that does. It could also be the year old 4f im using but its been stored in my closet all of the time and doesnt get used much. Just have to try one thing at a time for right now.

I don't think it is your 4F priming powder my 4F powder has to be5 years old think I still have a little less then 1/2 the can left.I would drill out your vent liner I here you say you use a vent nipple tool to clean out you vent liner sounds like the old t/c vent liners with the screw driver slot hole.The new improve vent liners have to be .070 .I would think take a old vent liner and open it up to .060 I use to drill out the t/c but I don't remember the drill size :another important thing to view is you vent liner is not below the priming powder pan and after firing the gun look and see if there is no smoke coming from the bottom of the trigger guard seen vent liners that are below the lock crack and split the stock in the lock area to to ignition under the lock itself.

I got the priming figured out now and its doing perfect. 6 shots today, all on a dirty bore, 4 were bulls eyes while my first 2 with 80 grains were low @ 100. I upped my charge to 90 and thats when my last 4 shots were in the orange. Still shot a 2" 4 shot group so im pretty happy with that. I find that if i reload right away and then check my target, i dont have the hard to load issue. As soon as the goex drys up, thats when im screwed and have to force the ball down the bore. Next year i am switching out my sights with something different so i can see the sights better. May just order sights from deer creek and ask for the ones that are on their northwest rifle, Those sights are clearer than day.

I find 5 shots max: before the patched ball start to get tight I use a wad under the patched RB I can go as many shots as I want no problem use one size bigger in wads like I use a 54 cal. in a 50 flinter and a 56 wad in my 54 flinter you may notice a big difference in tighter groups.

I'll pick up some wads next time i go to the store. If they have them that is We're lucky that the stores around here even carry powder.