Update app.py

app.py

@@ -689,7 +689,7 @@ def prep_and_save_data(index, skip_sample, completed: bool):
         base = st.session_state.data.iloc[index][COLS_TO_SAVE].to_dict()
 
     payload = {
-        **existing,  # previously saved stuff (extra keys, old schema, etc.)
+        **existing,
         **base,
         'user_id': st.session_state.user_id,
         'index': st.session_state.current_index,
@@ -840,15 +840,15 @@ elif st.session_state.current_index < len(st.session_state.data):
     show_fields(STEPS[step])
 
     c1, c2, c3 = st.columns([1,5,2])
-#    with c1:
-#        if st.button("<< Previous"):
-#            if step > 0:
-#                st.session_state.step -= 1
-#                st.rerun()
-#            else:
-#                st.session_state.current_index -= 1
-#                st.session_state.step = total_steps - 1
-#                st.rerun()
+    with c1:
+        if st.button("<< Previous"):
+            if step > 0:
+                st.session_state.step -= 1
+                st.rerun()
+            else:
+                st.session_state.current_index -= 1
+                st.session_state.step = total_steps - 1
+                st.rerun()
     with c2:
         label = " **Submit >>**" if step < total_steps - 1 else "**Submit & next session**"
         if st.button(label):