It seems like the build failures are related to timeouts of jmol. These timeouts started roughly at the time when the default Java version was changed in java-common from 10 to 11 in October 2018.
There are also other reports of jmol being broken depending on the jre version, see https://ask.sagemath.org/question/47837/jmol-stuck-at-initializing-3d-display/ While jmol was already replaced by threejs as the default 3d viewer in interactive mode, it is still used in the command line mode and hence when running the tests. Maybe we should try to remove jmol completely, or fix it on mipsel and mips64el. Best, Tobias
