The game doesn't summon entities on the right coordinates. When trying to spawn two Armour Stands or more on different coordinates, for some reason they spawn in the same place.

For example, these two commands have two different coordinates on the x-axis but spawn two armour stands on the same x coordinate.

/summon minecraft:armor_stand -221.5 88.5 -20 {NoGravity:1,CustomNameVisible:1b,CustomName:'{"text":"-221.5"}'}
/summon minecraft:armor_stand -222 88 -20 {CustomNameVisible:1b,CustomName:'{"text":"-222"}'}

I have attached a screenshot with 6 different armour stands. Each of them has a custom name showing their respective x-coordinate that was used in the command to spawn them (e.g. an armour stand with "-222" for the name was spawned on -222 88 -20). As you can see, the armour stand that was spawned on -222 88 -20 and the armour stand that was spawned on -221.5 88 -20 share the same spot even though they have different x-coordinates (both of these two armour stands are in the middle).
The furthest left and right armour stand clearly have the same distance from the middle armour stand "-222". The left armour stand "-221" is 1 block apart from the middle armour stand "-222" and the right armour stand "-222.5" is also 1 block apart from the middle armour stand even though the gap should be 0.5 blocks long since the armour stands weren't spaced out equally.

The commands that were used to summon the armour stands:

/summon minecraft:armor_stand -222 88 -20 {NoGravity:1,CustomNameVisible:1b,CustomName:'{"text":"-222"}'}

/summon minecraft:armor_stand -221.01 88.2 -20 {NoGravity:1,CustomNameVisible:1b,CustomName:'{"text":"-221.01"}'}

/summon minecraft:armor_stand -221.5 88.5 -20 {NoGravity:1,CustomNameVisible:1b,CustomName:'{"text":"-221.5"}'}

/summon minecraft:armor_stand -222.5 88 -20 {CustomNameVisible:1b,CustomName:'{"text":"-222.5"}'}

/summon minecraft:armor_stand -221.5 88.5 -20 {NoGravity:1,CustomNameVisible:1b,CustomName:'{"text":"-222.01"}'}

The seed: 5579261104843540928
Type of the world: custom empty world with forest biome.