[Bug]: Videos duplicate themselves when importing playlists

[Xindaris]

Guidelines

• I have encountered this bug in the latest release of FreeTube.
• I have encountered this bug in the official downloads of FreeTube.
• I have searched the issue tracker for open and closed issues that are similar to the bug report I want to file, without success.
• I have searched the documentation for information that matches the description of the bug I want to file, without success.
• This issue contains only one bug.

Describe the bug

1. Add videos to a playlist. (Using the quick bookmark feature; unsure if that's relevant)
2. Export the playlist.
3. Import the playlist on a different computer.
4. Add videos to the playlist on that other computer, and export again.
5. Import on the first computer.
6. Some videos randomly get two "copies" in the playlist now.

Expected Behavior

Playlists should merge properly when importing, and not add another copy of a video that's already in the playlist.

Issue Labels

inconsistent behavior, usability issue

FreeTube Version

v0.20.0 Beta

Operating System Version

Windows 11

Installation Method

.exe

Primary API used

Local API

Last Known Working FreeTube Version (If Any)

No response

Additional Information

No response

Nightly Build

• I have encountered this bug in the latest nightly build.

[lbpth]

It is also duplicated when I try to add video that has existed in the playlist before.

For example, I have playlist named Piano
1 - I add the video named Turkish March to Piano playlist then the number video is 1
2 - I click the button + again (still above Turkish March video), the number video count 2 in the Piano playlist
So, how to avoid duplicates if I have more than 100 videos in the playlist, manual removal is not good solution.