[MC-150287] Invulnerable Vexes in a stack with set Motion start to sink

The commands I used are:
(with no visible particles):

/summon vex -229.0 3 103 {NoGravity:0b,Invulnerable:1b,Tags:["DarkCloudBase"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Passengers:[{id:"minecraft:area_effect_cloud",Particle:"block air",ReapplicationDelay:0,Radius:10f,RadiusPerTick:0f,Duration:9999,WaitTime:0,Motion:[0.0,0.0,0.4],Tags:["DarkCloud"],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}],Effects:[{Id:7b,Amplifier:1b,Duration:1,ShowParticles:0b},{Id:9b,Amplifier:0b,Duration:100,ShowParticles:0b},{Id:15b,Amplifier:0b,Duration:40,ShowParticles:0b},{Id:20b,Amplifier:1b,Duration:40,ShowParticles:0b}]}]}

(Basically was a moving wall of particles, in a corridor, that kills you)

And:

execute as @e[tag=DarkCloudBase] run data merge entity @s {Motion:[0.0d,0.0d,0.05d]}

(on a repeating command block)

I am using a vex, rather than an armor_stand, because the Marker:1b tag no longer allows movement through walls and things. I notice that it also goes backwards and down slowly when its Motion is set to 0.

Even with no interaction from a survival mode player, it still randomly goes against its constantly set motion.

EDIT: Sorry the command comes out so big..