GraphicsMagick/libheif/vvdec issues not getting closed due to "Progression task errored out: Build setup failed"

There is a strange issue going on with GraphicsMagick issues related to libheif using the vvdec codec in that oss-fuzz is failing to automatically close issues. In all of these cases, the builds seem fine, and the issues no longer reproduce in builds that I create and test myself. The vvdec maintainers believe that they have addressed all of the issues that oss-fuzz says are still open.

When I look at the testcase detail (e.g. for issue [521915812](https://issues.oss-fuzz.com/issues/521915812) I see this error in the logs:

```
2026-06-09 06:46:42 UTC] oss-fuzz-tworker-1-cnxw: Fuzz task : Fuzzer libFuzzer_graphicsmagick_coder_HEIF_fuzzer generated testcase crashed in 124.0 seconds (r202606080645).
[2026-06-09 06:47:58 UTC] oss-fuzz-tworker-2-s4p7: Minimize task started.
[2026-06-09 07:37:03 UTC] oss-fuzz-tworker-2-3bq2: Minimize task finished.
[2026-06-09 07:37:45 UTC] oss-fuzz-tworker-1-rq1d: Regression task started.
[2026-06-09 07:57:47 UTC] oss-fuzz-tworker-2-38jn: Regression task started.
[2026-06-09 08:17:50 UTC] oss-fuzz-tworker-1-560f: Regression task started.
[2026-06-09 14:35:27 UTC] oss-fuzz-tworker-1-03nd: Regression task errored out: Timed out, current range r202605040702:r202605150600.
[2026-06-09 14:56:38 UTC] oss-fuzz-tworker-1-nmft: Regression task started.
[2026-06-09 15:07:03 UTC] oss-fuzz-tworker-2-5zq6: Regression task started.
[2026-06-09 15:17:04 UTC] oss-fuzz-tworker-2-tzh3: Regression task started.
[2026-06-09 19:54:21 UTC] oss-fuzz-tworker-1-gdx6: Regression task finished: regressed in range 202605040702:202605060640.
[2026-07-13 13:20:33 UTC] oss-fuzz-tworker-1-nbmn: Progression task started.
```
The 2026-06-09 date is a long time ago, and 2026-07-13 is today.

It seems as if the oss-fuzz infrastructure is not working. The testcase gets started but eventually it fails. I am not allowed to see "GCP Task Logs". If I download "task logs" I get an empty file?

How can this be solved?

Start with testcase 521915812 and compare the visible task timeline, especially the failed regression task and later progression task. Check the downloaded task logs and the GCP Task Logs access behavior to determine why the progression task reports a build-setup failure despite successful local builds. Done means identifying the infrastructure failure and restoring automatic issue closure.

Written by the indexing model from the issue text.