Splicing???

[Brion Toss]

Hello again,
6 to 8 yarns is what I said in the video, and since we made it I've upped that to 9 at each point; destruction tests showed that a splice tapered this way was at least as strong as one with fewer yarns pulled, and it was easier to run home. But still, it's unlikely to be the sole, or even the primary problem for you.
One other possible contributing factor is slack in the eye of the cover. As you run the splice home it is very easy for this to happen, and you need to get it out repeatedly as the splice goes home. Otherwise the core that has been dragged into the standing part (creating that slack) takes up room that the splice needs. So, is there any slack in the eye?
Finally, be sure to flex the spliced section smartly as things get sticky. Your can also pound that section with a wooden mallet to loosen the fibers.
Your other taper details sound right -- though I don't recall how far I said to bury the core. 14 diameters is right, and that's about 4 tracer lengths.
Fair leads,
Brion Toss