Mobs do not use correct rotational values in commands when idling

Iron Golems (Or any mobs). when executing commands that use rotational coordinates (^ ^ ^) do not use the proper rotational value. When the iron golem walks, commands that use rotational coordinates function as intended. However, when the iron golem idly rotates or looks at the player while standing still, the golem keeps the rotational value of the direction it last walked. 

To Reproduce:

1. Summon a golem, (or any mob) either through a /summon command or by building it

2. Use this command: 

   /execute at @e[type=minecraft:iron_golem] run particle minecraft:end_rod ^ ^1 ^3 .1 .1 .1 .001 200

1. As the iron golem walks, the command should function as intended.

2. After the iron golem has walked in a direction and stopped, wait for it to idly rotate or look in another direction, then execute the same command.

3. The particles will appear in the direction the iron golem last walked, not the direction it is currently facing.

4. For further evidence that this is due to the iron golem and not the command, here is another command that should accomplish the same task but again, reproduces the same bug: 

   /execute at @e[type=minecraft:iron_golem] positioned ^ ^ ^4 run particle minecraft:dust .6 0 1 1 ~ ~1 ~ .1 .1 .1 .0001 200

After experimenting with an iron golem, this issue seems to occur for ALL mobs, not just iron golems. Tested with a creeper and a zombie and the same issue occurs.

Here is a video demonstrating the bug as well:

https://www.youtube.com/watch?v=slfSd80sMeA&feature=youtu.be