Giving a CustomName to an entity in the form of a JSON array with two or more objects causes the last JSON object in the array to be duplicated.
When applying the following JSON
[{"text":"1","color":"#f73c20"},{"text":"2","color":"#f73c20"}]
To an entity with the following command
/summon minecraft:armor_stand ~ ~1 ~ {"CustomNameVisible":true,"CustomName":"[{\"text\":\"1\",\"color\":\"#f73c20\"},{\"text\":\"2\",\"color\":\"#20a8f7\"}]"}
Produces the following nametag
[media]
This happens on my system too. It appears that every colored string after the first is repeated.