This is just an inconvenient bug that has only affected one user, but it was very confusing to figure out what was going on.
This can be repro’d on meta by starting a draft of a topic and setting the category to anything, we’ll say
bug, refresh the page so the composer goes away but a draft is saved. Now change to a category that has restricted access, but is available for you to post in, in my case ‘plugins’. In this category the Open Draft button is greyed out with seemingly no way to open the draft. The only way to get the open draft button back is to go back to /latest or another category that doesn’t have restricted permissions.
Again, super rare problem that is low priority, but it did prevent the user from creating a post. I had to impersonate the user to figure out what was going on.