Hi Hans, With the latest LMTX (current version: 2020.11.13 19:13), a project (which used to typeset correctly until last week) cannot be typeset anymore. I did try to typeset smaller parts of my files but this did not help: I keep getting fatal error: return code: 11 and no PDF output. Somewhere in the log I have also error in line 35, namespace 'mathfences', instance 'curly', key 'curly,' where in my file \curly is defined as \definemathfence[curly][brace][command=yes,factor=auto] However this command works fine with LMTX when I use it in a minimal example. How can I get a more clear error message so that I can localize what the new LMTX does not like ? Of course I can stay with mkiv where my file can be typeset without problem, but it would be useful to have error messages which help really the user. Best regards: Otared K.