The bug
When an entity other than a player switches dimensions, its scoreboard values are removed.
To reproduce
/scoreboard objectives add Test dummy
/scoreboard objectives setdisplay sidebar Test
/scoreboard players set @e Test 1
/execute in the_nether run tp @e 0 128 0
→ ❌ Only your score remains.
This issue occurs as well when teleporting entities into the nether via a nether portal.
Related issues
is duplicated by
relates to
Comments

Can confirm for 19w40a.
Confirmed for 1.15-pre1.

Can confirm for 1.15.1.

can confirm for 1.15.2

can confirm for 20w11a

In 1.16.1

fixed in 20w45a
Cannot reproduce this issue in 20w49a.
Can confirm. Happens in 1.14.4 as well.