We are facing an issue with plugin locale in Cinema 4D R20. We use plugins.GeLoadString to load the strings. Till R19, this method used to fetch the data depending on the language selected in Cinema 4D. But in R20, it is selecting the data from the property file which comes first alphabetically. So we have strings_ES, strings_fr, strings_US, which means plugin is always loading with Spanish locale.
R20 uses a new scheme: https://developers.maxon.net/docs/Cinema4DCPPSDK/html/page_maxonapi_plugin_dev.html#page_maxonapi_plugin_dev_resources
We confirm @mp5gosu 's answer you have to use the new scheme with the R20.
edit : sorry I've marked @mp5gosu post as the solution, but it's still your decision to do so