[Bug]: Magenta line on top of H.265 video

### Which component impacted?

Encode

### Is it regression? Good in old configuration?

None

### What happened?

First example is a GStreamer pipeline with https://github.com/games-on-whales/gst-wayland-display:
```
$ GST_PLUGIN_PATH=./target/debug/ GST_GL_PLATFORM=egl gst-launch-1.0 waylanddisplaysrc ! 'video/x-raw(memory:DMABuf),width=1920,height=1080,framerate=60/1' ! vapostproc ! vah265enc ! vah265dec ! glimagesink
```

Second example is just with `videotestsrc`:
```
$ GST_GL_PLATFORM=egl gst-launch-1.0 videotestsrc ! 'video/x-raw,width=2160,height=1080,framerate=60/1' ! vapostproc ! vah265enc ! h265parse ! vah265dec ! glimagesink
```

Resizing the window seems to fix the issue for the `videotestsrc` pipeline, but the `waylanddisplaysrc` one is broken no matter what.

Also, while resizing more lines briefly appear for a moment:

Using `avdec_h265` and/or `videoconvert ! gtksink` changes nothing, also, `vaav1enc` and `vah264enc` are not affected.

### What's the usage scenario when you are seeing the problem?

Game Streaming

### What impacted?

_No response_

### Debug Information

```
$ vainfo
Trying display: wayland
Trying display: x11
vainfo: VA-API version: 1.22 (libva 2.22.0)
vainfo: Driver version: Intel iHD driver for Intel(R) Gen Graphics - 25.3.4 ()
$ eglinfo
...
OpenGL core profile vendor: Intel
OpenGL core profile renderer: Mesa Intel(R) Arc(tm) B580 Graphics (BMG G21)
OpenGL core profile version: 4.6 (Core Profile) Mesa 25.3.5-arch1.1
...
$ lspci -nn |grep -Ei 'VGA|DISPLAY'
03:00.0 VGA compatible controller [0300]: Intel Corporation Battlemage G21 [Arc B580] [8086:e20b]
```

[vainfo.log](https://github.com/user-attachments/files/25453883/vainfo.log)

[trace.tar.gz](https://github.com/user-attachments/files/25453881/trace.tar.gz)

### Do you want to contribute a patch to fix the issue?

No.