PaperMC/nms-patches/BlockJukeBox.patch

--- a/net/minecraft/server/BlockJukeBox.java
+++ b/net/minecraft/server/BlockJukeBox.java
@@ -140,6 +140,11 @@
         }
 
         public void setRecord(@Nullable ItemStack itemstack) {
+            // CraftBukkit start - There can only be one
+            if (itemstack != null) {
+                itemstack.count = 1;
+            }
+            // CraftBukkit end
             this.record = itemstack;
             this.update();
         }