Addon uploaded to Steam Workshop has no Date Modified

[HousePet]

This has happened to the last two Arcanum Class Pack updates.
The version that is on the Steam Workshop appears to have no Date Modified on the file, so Steam (or maybe ToME4) thinks that the Addon is never the current version and redownloads every time the game is run.
I am unsure if the file has a Date Created, as that gets overwritten with the time I download the Addon from the Workshop.
The Addon file on the te4.org repository does not have the same issue, so it appears to be something either going wrong with the tool that uploads it to Steam, or something wrong with Steam itself.
I can reupload the Addon, which has once fixed the issue, but that doesn't really address whatever is causing the issue.