When an armor stand is on the ground, updating its rotation via /tp
sometimes causes it to twitch and then remain facing the same direction visually.
To test:
/summon armor_stand ~ ~ ~
From chat:
/tp @e[type=armor_stand,c=1] ~ ~ ~ ~90 ~
Repeat step 2 from your chat over and over.
Notice that sometimes the armor stand fails to rotate visually.
Related issues
Comments

Relates to MC-103800