This is a problem I've noticed myself which I resolved. But my friend is in a situation where he cannot resolve it.
What happened to me was that my pendant was at +99 all stats. Then I added a new set from the Gold tier. Instead of it becoming +102 all stats, or +100 (because there is a 100 max limit now), it stayed at 99. Adding a new gold set did nothing.
So it looks like the server will ignore you adding a new set if it will make your pendant go over 100. So I tried a new thing, I added a new Purple tier set which adds +1. Bingo, my pendant became 100.
My friend's problem is that he has already maxed out all the Purple tier mobs. He is at +99 allstat right now and he has no way of making it 100, because there are no more Purple mobs for him to add. His IGN is Nanji.
What happened to me was that my pendant was at +99 all stats. Then I added a new set from the Gold tier. Instead of it becoming +102 all stats, or +100 (because there is a 100 max limit now), it stayed at 99. Adding a new gold set did nothing.
So it looks like the server will ignore you adding a new set if it will make your pendant go over 100. So I tried a new thing, I added a new Purple tier set which adds +1. Bingo, my pendant became 100.
My friend's problem is that he has already maxed out all the Purple tier mobs. He is at +99 allstat right now and he has no way of making it 100, because there are no more Purple mobs for him to add. His IGN is Nanji.