I tried to create a pack with 35 music discs but when I tried to play the music discs the first 15 didn't make a single sound and the other 20 discs just had the standard music disc 11 sound.
With the function command I found out the I can only spawn in the first 15 custom discs.
When I looked in the resource pack I found out that all the files were there but when I looked in the datapack folder I found out that again only the first 15 were processed. It did not help when I tried to redo the process it kept on processing the first 15.
If anyone needs more information just say it, will try to respond as fast as possible.

My bad, placed the datapack in the wrong world with 1 letter difference in it's name