diff --git a/src/connectors/mysql_connector.py b/src/connectors/mysql_connector.py
index 0250493..f763e6a 100644
--- a/src/connectors/mysql_connector.py
+++ b/src/connectors/mysql_connector.py
@@ -301,18 +301,21 @@ class MySQLConnector:
                             current_group.append(row)
                             current_key = key
 
-                        # At end of batch: handle final group
+                        # At end of batch: ALWAYS yield complete groups immediately
+                        # Incomplete groups at batch boundary will be continued in next batch
+                        # because we track last_key correctly for resume
                         if not rows or len(rows) < limit:
                             # Last batch - yield remaining group and finish
                             if current_group:
                                 yield current_group
                             return
                         else:
-                            # More rows might exist after this batch
-                            # Check if the last row in this batch has same key as current_group
-                            # If yes, DON'T yield yet - the group might continue in next batch
-                            # If no, yield because we know the group is complete
-                            if rows:
+                            # More rows exist - yield all COMPLETE groups seen so far
+                            # If current_group is incomplete (same key as last row), keep buffering it
+                            if current_group:
+                                # Check if this is a complete group or partial
+                                # Complete group: all rows with this key have been seen in this batch
+                                # Partial: might continue in next batch
                                 last_row = rows[-1]
                                 last_row_key = (
                                     last_row.get("UnitName"),
@@ -321,16 +324,29 @@ class MySQLConnector:
                                     last_row.get("EventTime")
                                 )
 
-                                # If last row has different key than current group, current group is complete
-                                if last_row_key != current_key and current_group:
+                                if last_row_key != current_key:
+                                    # Current group is complete (ended before batch boundary)
                                     yield current_group
                                     current_group = []
                                     current_key = None
-                                # else: same key as current_group, so continue in next iteration
+                                # else: current group continues past batch boundary
+                                # Keep it in current_group for merging with next batch
+                                # BUT we need to update last_key to be the LAST yielded key,
+                                # not the current incomplete key, so resume works correctly
+                                # Actually NO - we should NOT update last_key if we have a pending group!
 
-                        # Update last_key for next iteration
-                        if current_key:
-                            last_key = current_key
+                            # Update last_key only if we don't have a pending incomplete group
+                            if current_key is None and rows:
+                                # All groups in this batch were yielded and complete
+                                last_row = rows[-1]
+                                last_key = (
+                                    last_row.get("UnitName"),
+                                    last_row.get("ToolNameID"),
+                                    last_row.get("EventDate"),
+                                    last_row.get("EventTime")
+                                )
+                            # If current_key is not None, we have incomplete group - DON'T update last_key
+                            # so next iteration will continue from where this group started
 
                         break  # Success, exit retry loop