My actions:

1. Spawn an armor stand with a shulker as a passenger on non-integer coordinates (I used: "summon minecraft:armor_stand ~ ~-2.235 ~ {NoGravity:1b, Small:1b, Passengers:[ {id:"minecraft:shulker", NoAI:1, PersistenceRequired:1, Peek:0b}

   ] }  ").

1. Try to stand and move on the top of the shulker.

My screen is shaking in this situation. The same bug is in 1.14.4, but in 1.13.2 it is ok and no bug appears.

All my actions and problem are in the video.

P.S. In the video there are other command blocks around me. But the bug appears even in new world. I play without any modifications and datapacks.