GraphQL error: Internal server error
 

Starting around XC 5.4.1.3x something, I started getting this whenever I try to upgrade.

GraphQL error: Internal server error; Can't start redeploy because other process is in progress

Until then it was smooth upgrades for the last 3 or 4 years. I put in a ticket when it happened a few months ago, the got it out of that mode, but it just started doing it all over again.

I have another ticket in so I'm sure they'll fix it but…anyone know what this is about?

Re: GraphQL error: Internal server error
 

Cart started some upgrade and did not finish properly so there are left over files. Now it thinks it has to continue with that upgrade but it cannot as it doesn't exists anymore.
There are few files you can remove from var directory for "scenario" and this usually fixes it.
You can also run the rebuild from the command line and this may fix it as well. Although it runs the same processes there is a difference between running it from admin and from the command line - when form command line you are not logged in to admin so the rebuild runs as clean as possible.