Label track deleted after Tempo (or Time Signature)change and closing project (without saving)

[LinkeHand]

Bug description

Make a tempo change in the time signature toolbar to a project with a label track.
Close the project without saving.
The label track is deleted.

The result is even worse than in issue #6166, where the label track is only not in sync.

Steps to reproduce

1. Generate Track
2. Add Label Track
3. Save Project - Save to computer
4. Close and reopen the file
5. Change Tempo (or Time Signature) in the Time Signature Toolbar
6. Close file - without saving
7. Reopen file

Expected behavior

Closing a project does not change the project file at all.

Actual behavior

After Step 4:

After Step 5 - tempo changed:

After Step 6 - reopened project file which was previously only closed without saving:

Audacity Version

current master / alpha / nightly build

Operating system

Windows

Additional context

Tested with Audacity 3.6.0-alpha-20240514 (audacity-win-3.6.0-alpha-20240514+3af928c-x64-msvc2022.zip).

[petersampsonaudacity]

Testing on W11 with the 3,6.0 Beta build:

I confirm this bug - the error also occurs if you change the Time Signature at @LinkeHand 's Step 5 (I updated the STRs and bug title).

And testing shows that it is a regression on 3.5.1

[petersampsonaudacity]

@dozzzzer

This issue (and it's close cousin #6166 ) are both pretty serious issues as thee involve "silent"/hidden data loss for the user. And as the loss occurs as the project is closed the data loss they may not be discovered by the user till much layer.

I think that these two bugs really deserve a fairly high P-rating, do you agree?

[LinkeHand]

I made tests with try and error for bug #6453 (not #6166):

• audacity-win-3.6.0-alpha-20240404+cccbd6c-x64-msvc2022 --> the label track is not deleted
• audacity-win-3.6.0-alpha-20240404+983dc1b-x64-msvc2022 --> the label track is deleted

As far as I see, there is no further version between theese two builds. Perhaps it helps.

[LinkeHand]

accidentally closed