PaperMC/nms-patches/BlockJukeBox.patch

--- a/net/minecraft/server/BlockJukeBox.java
+++ b/net/minecraft/server/BlockJukeBox.java
@@ -143,6 +143,11 @@
         }
 
         public void setRecord(ItemStack itemstack) {
+            // CraftBukkit start - There can only be one
+            if (!itemstack.isEmpty()) {
+                itemstack.setCount(1);
+            }
+            // CraftBukkit end
             this.record = itemstack;
             this.update();
         }