Vindicators with a totem in thier off-hand won't die after the totem is used

While making Johnny vindicators, zombie pigmen, and wither skeletons fight, I noticed that after changing the item in the vindicator's off-hand to a totem of undying, after the totem was used and the vindicator died again, would occasionally (maybe 1/15 vindicators) stay in the death animation on the floor and continue moving around and fighting. The only way to stop this would be running a /kill @e command. This is somewhat ruining my mob fights and would greatly appreciate it being fixed soon. Thanks!

How to recreate (how I discovered)

1. get a vindicator and name it Johnny
2. put down 3 command blocks
3. set them all to repeat and have two on a 750 tick delay, one on a 100 tick delay
4. in the first 750 tick delay command block input the following command: /replaceitem entity @e [name=Johnny] slot.weapon.offhand 1 totem
5. in the second 750 tick delay command block input this command: /replaceitem entity @e [name=Johnny] slot.weapon.mainhand 1 diamond_axe
6. and finally, in the 100 tick delay command block, put this command: /effect @e [name=Johnny] instant_health 1 1

these are the exact conditions that were in play when I first noticed this bug. Have the Johnnys be killed by a pigman or wither skeleton (was mainly a wither skeleton which had strength 3, a diamond sword, a full set of diamond armor, and a totem in its off-hand) a few times and it should happen. Could also be partially due to lag when the vindicator died as there were many entities fighting when this was all hapening.