Steps to replicate the issue (include links if applicable):

• I am uploading media with UploadWizard with a long name
• "Describe" step checks on name work perfectly, while "Publish" step checks fail
• I am unable to go back to "Describe" step, fix the name, and re-try publishing

What happens?:
Apparently the first check considers only the file name itself, while the other one considers filename plus extension. Then, the file name length test may pass on the "Describe" page, but then may fail at publishing stage.

Moreover, when the error happens at publishing stage, there seems to be no way to go back and fix the file name. I am then forced to re-do the whole upload, losing all data inserted meanwhile.

What should have happened instead?:
UploadWizard should:

• warn me that the title is too long at "Describe" step
• allow me to go back to "Describe" step, if there are problems at the "Publish" step

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):
Wikimedia Commons

Other information (browser name/version, screenshots, etc.):

Reformulated from this discussion.