Arcade Leaderboards (VDA) - Can't make them work correctly

We have a problem with getting Viveport Arcade Leaderboards working correctly.
We thought the method:   
ArcadeLeaderboard.UploadLeaderboardScore(OnScoreUploadedHandler, leaderboardFullName, GameInfo.PlayerName, _playerScore);

should save a new Score for every different PlayerName. For now, it works like the non-arcade leaderboard, updating the entry only once the other player has the better score than the previous one instead of adding the new entry.
PS
1.We have switched to Arcade mode using Arcade Switch tool. 
2. We use Unity3d 

It would be perfect to get some answer soon, as ideally, we would like to include this feature in VDA submission.

[HackPerception]

, Can you please lend a hand on this? 

[yakingkuo]

Hi Marcin: 

Please check attached screen shot.  I would like to know what the "Update type" field on the developer console you choose for Arcade Leaderboard. Thanks a lot.

 

We are using Append.

I don't know how this happened but it seemed that it wasn't working yesterday. (I was always seeing one entry in the leaderboards).

Today I checked it, and it downloaded all entries that I was trying to save yesterday.

Thank you so much for quick reply.

Also now I can see that some of the records have name "Viveport User". 
I'm quite sure I did not save any score entries with such name. Do you how why it works like that? 
Do you default the name to Viveport user in some case?

Also is the sessions implementation required for local leaderboards to work correctly?