here the solution (or workaround) from the openandromaps team:
1) download the file osmarender.xml from here
2) Create a new folder (e.g. basic_theme) in /oruxmaps/mapstyles/
3) copy file osmarender.xml to /oruxmaps/mapstyles/basic_theme
Now you can use the orux themeswitcher to switch back to the orux standard mapstyle (orux basic theme)
Regards,
outdoor_max