Okay we use -9ms here because this counters the +9ms folks add to their charts. Ensure we clear the series map when freeing songs

src/ScreenOptionsMasterPrefs.cpp

@@ -712,7 +712,7 @@ static void GlobalOffsetSeconds( int &sel, bool ToSel, const ConfOption *pConfOp
 
 static void MachineSyncBias( int &sel, bool ToSel, const ConfOption *pConfOption )
 {
-	constexpr std::array<float, 2> mapping = { 0.0f, 0.009f };
+	constexpr std::array<float, 2> mapping = { 0.0f, -0.009f };
 	MoveMap( sel, pConfOption, ToSel, mapping.data(), mapping.size() );
 }
 

src/SongManager.cpp

@@ -599,6 +599,7 @@ void SongManager::FreeSongs()
 
 	m_pSongs.clear();
 	m_mapNameToGroup.clear();
+	m_mapSeriesToGroups.clear();
 	m_SongsByDir.clear();
 
 	// also free the songs that have been deleted from disk