You should be able to start things back up with
./launcher start app
and then make your backup!
I also just got a rebuild error related to yarn:
"lodash@4.17.21\" is incompatible with request
ed version \"lodash@4.17.15\"", "warning \" > @mixer/parallel-prettier@2.0.1\" has unmet peer dependency \"prettier@^2.0.0
I’m looking further to see what it might be.
I just rebuilt again and it worked, so perhaps something that was broken got fixed…so you might just try to rebuild again after you make that bacukp!