https://github.com/Beep6581/RawTherapee/issues/6452

Index: rtgui/cacheimagedata.cc
--- rtgui/cacheimagedata.cc.orig
+++ rtgui/cacheimagedata.cc
@@ -78,7 +78,7 @@ CacheImageData::CacheImageData() :
  */
 int CacheImageData::load (const Glib::ustring& fname)
 {
-    setlocale(LC_NUMERIC, "C"); // to set decimal point to "."
+    //setlocale(LC_NUMERIC, "C"); // to set decimal point to "."
 
     Glib::KeyFile keyFile;
 
