Add-on generated structures will not generate mobs

This has been a minor issue for a while now but what happens is I create a structure with entities/mobs within the structure and save the build to a file using a structure block. If I generate the file saved with a regular structure block the build loads normally with the entities still in. However, when i try to load the structure using add-ons (features generation) the build generates normally but entities I saved with the structure are not loaded. This also occurs when I try to load the build with “/structure example ~ ~ ~”. I have tried everything to make it work but I keep getting the same results.