File format exception when using Push Package(s) to Octopus

[grjw]

I am using Hosted Azure DevOps and the Octopus marketplace extension

For my build pipeline:

I am doing a "dotnet publish" step, using .NetCore task:

I then have Publish build artifacts step

Here is the artifact from my build

For my release pipeline

I am defining an artifact with Source Alias of "_Dynamics Integrations", linked to the build

For my Push package(s) to Octopus step (version 7.*):

I am receiving this

2026-02-11T15:17:53.3411635Z ##[section]Starting: Push Packages to Octopus
2026-02-11T15:17:53.3422474Z ==============================================================================
2026-02-11T15:17:53.3422604Z Task         : Push Package(s) to Octopus
2026-02-11T15:17:53.3422673Z Description  : Push your NuGet or Zip package to your Octopus Deploy Server. **v6 of this step requires Octopus 2022.3+**
2026-02-11T15:17:53.3422796Z Version      : 7.0.1319
2026-02-11T15:17:53.3422858Z Author       : Octopus Deploy
2026-02-11T15:17:53.3423290Z Help         : Version: 7.0.1319. [More Information](https://g.octopushq.com/TFS-VSTS)
2026-02-11T15:17:53.3423396Z ==============================================================================
2026-02-11T15:17:54.2126554Z Uploading package, a.zip...
2026-02-11T15:17:54.4763902Z ##[error]"Failed to execute push. Error: There was a problem with your request.
File format exception
Error: Error: There was a problem with your request.
File format exception
    at e.<anonymous> (D:\a\_tasks\OctopusPush_d05ad9a2-5d9e-4a1c-a887-14034334d6f2\7.0.1319\index.js:19:11517)
    at d (D:\a\_tasks\OctopusPush_d05ad9a2-5d9e-4a1c-a887-14034334d6f2\7.0.1319\index.js:19:9080)
    at Object.next (D:\a\_tasks\OctopusPush_d05ad9a2-5d9e-4a1c-a887-14034334d6f2\7.0.1319\index.js:19:8363)
    at p (D:\a\_tasks\OctopusPush_d05ad9a2-5d9e-4a1c-a887-14034334d6f2\7.0.1319\index.js:19:7921)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
2026-02-11T15:17:54.4874369Z ##[section]Finishing: Push Packages to Octopus

If I download the a.zip from the DevOps UI,. it unzips fine. so I can't see why the format is invalid
If I change the package string in any way it says File Not Found, so I think i'm linking to the file correctly

[grjw]

I changed my build process to zip the binaries using the Archive Files task and it now pushes the files to Octopus fine.

Interestingly the zip file size has shrunk from 12mb to 9.7mb, so the dotnet zip step is producing zips in a strange format