Deployment fails with no error message when test artifacts are present

First of all, I am aware that there are 2 similar-looking issues already open, but this is different: for me, the deployment step fails without any error message, whereas the other issues refer to situations where the CI log says "Deployment failed".

I added Cypress tests to my build process about a week ago, and initially it worked. Then I added visual snapshots to my tests, which produce .png artifacts, as well as the .mp4 ones normally generated by Cypress. I am skipping these tests on my master branch (via a Node.js script), but the snapshots are always there. This leads to 2 situations:
- PR previews run the tests ok, but fail on deployment - no error message, it just stops after uploading the test artifacts
- master branch skips tests, but also fails on deployment - again no error message, it just stops after uploading the test artifacts

For the master branch, this is the entire log output for the deployment step:


If I remove the "test" step from the build entirely, it works just fine. This is really concerning, since a significant part of CI is to run tests, and it's exactly what I cannot do.

Start by reproducing the deployment step with Cypress-generated .png and .mp4 test artifacts, comparing a PR preview with the master branch where tests are skipped. Done means deployments complete successfully with these artifacts, or the deployment step reports a useful error instead of stopping after artifact upload.

Written by the indexing model from the issue text.