Entities (except players) get their scores reset when they change dimensions.

When I teleport an armorstand from the overworld to the nether, their scoreboard scores gets reset. This is the case for all entities except players.

For example:

/scoreboard objectives add test dummy

/scoreboard objectives setdisplay sidebar test

/summon minecraft:armor_stand ~ ~1 ~ {Tags:["test"],Invulnerable:1,NoBasePlate:1,NoGravity:1,CustomName:"{\"text\":\"test\"}",CustomNameVisible:1}

/scoreboard players set @e[tag=test] test 1

tp with:

/execute in minecraft:the_nether run tp @e[tag=test] 0 130 0

or:

/tp @e[tag=test] player

if the player is in the nether.