found error in filenames.

One array was too short. This had nothing to do with long filenames, other than if they were 12 characters exactly, which could only happen if the extension and the text before were filled completely

Marlin/Configuration_adv.h

 // be commented out otherwise
 #define SDCARDDETECTINVERTED 
 
+#ifdef ULTIPANEL
+ #undef SDCARDDETECTINVERTED
+#endif
 //===========================================================================
 //=============================Buffers           ============================
 //===========================================================================

Marlin/cardreader.cpp

  
   while (parent.readDir(p) > 0)
   {
-    if( DIR_IS_SUBDIR(&p) && lsAction!=LS_Count && lsAction!=LS_GetFilename)
+    if( DIR_IS_SUBDIR(&p) && lsAction!=LS_Count && lsAction!=LS_GetFilename) // hence LS_SerialPrint
     {
 
       char path[13*2];

Marlin/cardreader.h

   bool saving;
   bool sdprinting ;  
   bool cardOK ;
-  char filename[11];
+  char filename[12];
   bool filenameIsDir;
   int lastnr; //last number of the autostart;
 private: