Difference in output of .ds files- 1.2 vs 1.3

### Bug Summary
Playing the same project back in 1.2.0 and 1.3 alpha, there is an audible difference in the output. This difference translates to exports too. The difference is apparent in .ds samples (to be more specific, it is most apparent in the TR909Clap.ds sample), but my ears cannot tell the difference on most others. I believe this issue is limited to .ds files.

#### Steps to reproduce
1. Download project file from https://drive.google.com/file/d/1y6NeRq3Af7EZxFmGUl-KGL9QQSWuEfyG/view?usp=sharing
2. Play back in 1.2.0 vs playing back in 1.3 alpha
3. Audible mild difference.
4. Export
5. Audible mild difference.

For anyone who cannot export from both, etc:
https://drive.google.com/file/d/10prICuiS2nxaD-fqeS6dwk343-ttSQkd/view?usp=sharing (1.2.0)
https://drive.google.com/file/d/1AOR54ikabHOV8U_2CjM4lYNwBwDboNAy/view?usp=sharing (1.3 alpha)
Above are the reference WAVs.
If you cannot hear the difference, it is more apparent in the following set of links:
https://drive.google.com/file/d/1aceADoxwerhCMki5eVjCJzP_p_cA8iii/view?usp=sharing (1.2.0), https://drive.google.com/file/d/11cuVR5OvYEwQXyA_h21wtAJiMkPQC_pO/view?usp=sharing (1.3)
These are exports of a different project.

#### Expected behavior
They should sound the same.

#### Actual behavior
They sound different

#### Screenshot

#### Affected LMMS versions

1.2(.0), 1.3 alpha.

Start by reproducing the difference with the linked project and reference WAVs in LMMS 1.2.0 and 1.3 alpha, focusing on the TR909Clap.ds sample and both playback and export. No files, tests, or entry points are named, so trace the project’s .ds sample handling and audio-rendering path; done means identical output across both versions.

Written by the indexing model from the issue text.