Hearthstone metadata api gives inconsistent results

The Hearthstone (battlegrounds, region eu) metadata api gives inconsistent results.
When calling /hearthstone/metadata?locale=en_US&gameMode=battlegrounds
I get inconsistent results.
The gameModes property has different content:

Either:

Instance one

“gameModes”: [
{
“slug”: “constructed”,
“id”: 1,
“name”: “Constructed”
},
{
“slug”: “battlegrounds”,
“id”: 2,
“name”: “Battlegrounds”
},
{
“slug”: “arena”,
“id”: 3,
“name”: “Arena”
},
{
“slug”: “duels”,
“id”: 4,
“name”: “Duels”
},
{
“slug”: “standard”,
“id”: 5,
“name”: “Standard”
},
{
“slug”: “classic”,
“id”: 6,
“name”: “Classic”
},
{
“slug”: “mercenaries”,
“id”: 7,
“name”: “Mercenaries”
}
]

or

Instance two

“gameModes”: [
{
“slug”: “constructed”,
“id”: 1,
“name”: “Standard & Wild Formats”
},
{
“slug”: “battlegrounds”,
“id”: 2,
“name”: “Battlegrounds”
},
{
“slug”: “arena”,
“id”: 3,
“name”: “Current Arena Cards”
},
{
“slug”: “duels”,
“id”: 4,
“name”: “Current Duels Cards”
},
{
“slug”: “standard”,
“id”: 5,
“name”: “Standard”
},
{
“slug”: “classic”,
“id”: 6,
“name”: “Classic”
},
{
“slug”: “mercenaries”,
“id”: 7,
“name”: “Mercenaries”
}
]

Note the different name property on id 1, 3 and 4.
This back and forth has been going on for 12+ hours.

This makes it difficult to know when data is updated, and when to query the API for updates.

Related question: Is there an endpoint I can call to get the version of Hearthstone (game client, cardset version, api version or some way to determine what version is active, and if I have the latest data?