Transitions show wrong video

[KHouse75]

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OS and Version (please complete the following information):

• Operating System: Linux Mint 22.1 Xia
• Shotcut Version: 25.05.11, Flathub Flatpak

Describe the bug
Dissolve transitions will randomly show video from other portions of the project instead of the transition video from one segment to the other. I don't use other transitions so I do not know if it happens with others. The exported video also contains the wrong transitions. It's not all transitions in a project that will do this. Others will be perfectly fine.

When this happens, the same video in the incorrect transition will also appear in other transitions. Different transitions in other portions of the project may have a completely different incorrect transition and it will repeat for other transitions. Seems like they happen in groups.

I've seen this on different Linux OS versions and and different hardware as well as older shotcut versions. I'm pretty certain that this same issue occurred when I ran shotcut on windows.

Steps To Reproduce
Unknown. I'll be working on a project and all looks good. I'll export and notice it in the exported video or while reviewing from shotcut.

Expected behavior
Dissolve transitions should be a dissolve of the previous segment and the next segment.

Screenshots

Ripple_Issue-2025-08-21_23.57.38.mp4

[KHouse75]

A little more info on this issue. While it happens with VBR video quite often, it also happens with CBR although less often.