Broken workflow after update, import fails

I recently upgraded from version 4.7.7 to version 5.1.2. One of my workflows is not recognized as a workflow anymore. So it appears as a folder instead of having the workflow icon in the KNIME explorer. Not sure how I can fix it.

I tried to import the workflow via Import > “Select root directory” > Next. KNIME recognizes the nodes, but when I click Next, it tells me to fix invalid names. It seems that all nodes with a “#” are a problem. I can type in a new name, but I cannot even click Next or Finish, since they are greyed out, so something is broken here I suppose.

Hi,
It seems like your workflow.knime file is missing. It should be part of your workflow directory and when it is present KNIME recognizes the folder as a workflow. What is happening in your case, I think, is that you want to import the workflow, but because the file is missing, KNIME treats each subfolder (the nodes) as workflows or components instead. In the import view’s tree view you should never see individual nodes, only workflows, components, and data files.
Kind regards,
Alexander

It seems like I have to rebuild the workflow from scratch. It’s very strange that it got corrupted.