I saw that but thought, hey, its years ago - maybe it's fixed - but not :-(
I've done all I can to try to find the problem and it seems to come down to the ide. I've tried different versions of Java (Oracle and OpenJDK) but both the same (almost) errors when the source files are on a NAS.
I checked the directory structure both before compiling and after and all the files - no differences. I can't go any further with my diagnosis.
A pity, it would have made life so much easier and also I guess for any team development.