Don't use rmdir_r but roll our own version.

src/FSCommon.cpp

@@ -28,6 +28,34 @@ void listDir(const char * dirname, uint8_t levels)
 #endif
 }
 
+void rmDir(const char * dirname)
+#ifdef FSCom
+{
+    File root = FSCom.open(dirname);
+    if(!root){
+        return;
+    }
+    if(!root.isDirectory()){
+        return;
+    }
+
+    File file = root.openNextFile();
+    while(file){
+        if(file.isDirectory() && !String(file.name()).endsWith(".")) {
+            file.close();
+            rmDir(file.name());
+            FSCom.rmdir(file.name());
+        } else {
+            file.close();
+            FSCom.remove(file.name());
+        }
+        file.close();
+        file = root.openNextFile();
+    }
+    file.close();
+#endif
+}
+
 void fsInit()
 {
 #ifdef FSCom

src/FSCommon.h

@@ -27,3 +27,5 @@ using namespace Adafruit_LittleFS_Namespace;
 #endif
 
 void fsInit();
+void listDir(const char * dirname, uint8_t levels);
+void rmDir(const char * dirname);

src/mesh/NodeDB.cpp

@@ -91,7 +91,7 @@ bool NodeDB::resetRadioConfig()
     if (config.device.factory_reset) {
         DEBUG_MSG("Performing factory reset!\n");
         // first, remove the "/prefs" (this removes most prefs)
-        FSCom.rmdir_r("/prefs");
+        rmDir("/prefs");
         // second, install default state (this will deal with the duplicate mac address issue)
         installDefaultDeviceState();
         // third, write to disk