diff --git a/src/calibre/devices/kindle/apnx.py b/src/calibre/devices/kindle/apnx.py
index ee519750e0..178c1091f3 100644
--- a/src/calibre/devices/kindle/apnx.py
+++ b/src/calibre/devices/kindle/apnx.py
@@ -164,7 +164,7 @@ class APNXBuilder(object):
                 if c == '/':
                     closing = True
                     continue
-                elif c in ('d', 'p'):
+                elif c == 'p':
                     if closing:
                         in_p = False
                     else:
diff --git a/src/calibre/ebooks/metadata/extz.py b/src/calibre/ebooks/metadata/extz.py
index 1bda263015..021450fca5 100644
--- a/src/calibre/ebooks/metadata/extz.py
+++ b/src/calibre/ebooks/metadata/extz.py
@@ -70,7 +70,7 @@ def set_metadata(stream, mi):
     # Update the metadata.
     old_mi = opf.to_book_metadata()
     old_mi.smart_update(mi)
-    opf.smart_update(metadata_to_opf(old_mi))
+    opf.smart_update(metadata_to_opf(old_mi), replace_metadata=True)
     newopf = StringIO(opf.render())
     safe_replace(stream, opf_path, newopf, extra_replacements=replacements, add_missing=True)
 
diff --git a/src/calibre/gui2/library/views.py b/src/calibre/gui2/library/views.py
index 26f6788a75..1cfb04921d 100644
--- a/src/calibre/gui2/library/views.py
+++ b/src/calibre/gui2/library/views.py
@@ -439,10 +439,16 @@ class BooksView(QTableView): # {{{
 
         if tweaks['sort_columns_at_startup'] is not None:
             sh = []
-            for c,d in tweaks['sort_columns_at_startup']:
-                if not isinstance(d, bool):
-                    d = True if d == 0 else False
-                sh.append((c, d))
+            try:
+                for c,d in tweaks['sort_columns_at_startup']:
+                    if not isinstance(d, bool):
+                        d = True if d == 0 else False
+                    sh.append((c, d))
+            except:
+                # Ignore invalid tweak values as users seem to often get them
+                # wrong
+                import traceback
+                traceback.print_exc()
             old_state['sort_history'] = sh
 
         self.apply_state(old_state)