Saving skill points for next level

Hi there,

Quick question. I want to take my level 15 perk that costs 6 skill points. However, the most I've been getting per level up (past level 15) is 4 skill points. It would seem that this requires me to save 2 leftover skill points so that the next time I level up, I have 6 skill points. However, in practice, these skill points seem to vanish. I am currently down 6 skill points (after saving 2 from L15-L16 and only having 2 total when leveling up, and then saving 4 from L16-L17 and only having 4 total the following level up).

Is there a process I'm missing here? Sorry for the confusing question, just trying to figure out how I'm supposed to save up enough points to take a 6-point perk. Also a little annoyed about my missing 6 skill points but hopefully I'm not just understanding how the system works.

My brother reported the same thing
Said he saved 2 points from a previous level up, then only had 2 points total at the new level up

Now my only explanation
When you finish a battle, even if you didn't reach a new level, the leveling up menu will come up, allowing you to spend the accumulated points
Maybe you did save 2 at lvl 16, but did'nt level up the next battle
Then save 4 at lvl 17 , and not leveling up the next battle

You can save up AP at any time. Your case is just a simple coincidence: You gain less AP/level the more you level up. You start with 5 AP/level levels 1-10, then 4 AP levels 10-20 then 3 AP levels 20-40, and 2 AP from level 40 onward. There is also a misleading text at the end of the battle, saying "you gained a new level" even when you didn't but have unspent AP.