https://www.icyphoenix.com/viewtopic.php?f=29&t=725&p=5973#p5973
-----------------------------------
TheSteffen
Tue 19 Dec, 2006 08:50

Re: While Merging Two Topics...
-----------------------------------
OK,

find in 

OPEN [b]modcp.php[/b]
FIND
[codeblock]
//<!-- BEGIN Unread Post Information to Database Mod -->
								if($userdata['upi2db_access'])
								{
									$sql = "DELETE FROM " . UPI2DB_UNREAD_POSTS_TABLE . "
										WHERE topic_id IN ($topic_id_sql)";

									if ( !$db->sql_query($sql) )
									{
										message_die(GENERAL_ERROR, 'Could not delete topic reads', '', __LINE__, __FILE__, $sql);
									}

									$sql = "DELETE FROM " . UPI2DB_LAST_POSTS_TABLE . "
										WHERE topic_id IN ($topic_id_sql)";

									if ( !$db->sql_query($sql) )
									{
										message_die(GENERAL_ERROR, 'Could not delete topic reads', '', __LINE__, __FILE__, $sql);
									}
								}
//<!-- END Unread Post Information to Database Mod -->
[/codeblock]
REPLACE WITH
[codeblock]
//<!-- BEGIN Unread Post Information to Database Mod -->
					if($userdata['upi2db_access'])
					{
						/*
						$sql = "DELETE FROM " . UPI2DB_UNREAD_POSTS_TABLE . "
							WHERE topic_id IN ($topic_id_sql)";
						*/
						$sql = "DELETE FROM " . UPI2DB_UNREAD_POSTS_TABLE . "
							WHERE topic_id IN ($topic_id_list[$i])";

						if ( !$db->sql_query($sql) )
						{
							message_die(GENERAL_ERROR, 'Could not delete topic reads', '', __LINE__, __FILE__, $sql);
						}

						/*
						$sql = "DELETE FROM " . UPI2DB_LAST_POSTS_TABLE . "
							WHERE topic_id IN ($topic_id_sql)";
						*/
						$sql = "DELETE FROM " . UPI2DB_LAST_POSTS_TABLE . "
							WHERE topic_id IN ($topic_id_list[$i])";

						if ( !$db->sql_query($sql) )
						{
							message_die(GENERAL_ERROR, 'Could not delete topic reads', '', __LINE__, __FILE__, $sql);
						}
					}
//<!-- END Unread Post Information to Database Mod -->
[/codeblock]

For me it's working.

I have updated this http://www.phpbbxs.eu/viewtopic.php?t=693


