How to reproduce

• Summon 3 armor stands

  summon minecraft:armor_stand ~ ~ ~ {CustomName:"\"Main\"",CustomNameVisible:1b,Tags:["foo"]}
  summon minecraft:armor_stand ~1 ~ ~ {CustomName:"\"One\"",CustomNameVisible:1b,Tags:["bar"]}
  summon minecraft:armor_stand ~2 ~ ~ {CustomName:"\"Two\"",CustomNameVisible:1b,Tags:["bar"]}
  

• make 2 functions

  #to:foo
  execute as @e[tag=foo] at @s as @e[tag=bar,sort=nearest] run function to:say
  
  #to:say
  say Hello
  

• /reload and run /function to:foo in chat
  → Notice that "Two" prints its name in chat before "One" while it is further away

Note: When replacing sort=nearest with sort=furthest "One" will print its name first confirming the bug that they are swapped.