Enderman's spawner bug

Hi mojang team! I recently updated the minecraft from 1.12.0.28 to version 1.13.0.15 (beta) and well I found a fairly large bug and it is the following ... I had my pretty efficient endermans farm that generated between 75 to 100 endermans in 4 average minutes (that when I was at 1.12.0.28) now that I am at 1.13.0.15 it literally generates me between 5 to 20 endermans with 4 minutes in the waiting area ... and well I wanted to know if it is a bug oo something that does not generate well. It should be noted that I already tried 3 different farms and none is efficient.

Pd: There is a bug that makes books, armor and other enchanted objects look dull.

 

Thanks and hopefully fix the bug.