> NOTE: I am using a master with server version 5.6 with a slave which has the version 5.5 could this be the issue?
It is unsafe to have the Master be on a newer version than the Slave. (No, I cannot say that this is the cause of your problem.)
1236 is mentioned often:
1236 -
http://forums.mysql.com/read.php?10,275515 (Replication fun)
impossible position, sync_binlog -
http://forums.mysql.com/read.php?26,577600 (Got fatal error 1236 from master when reading data from binary log)
http://forums.mysql.com/read.php?26,565208 (error 1236 - missing file, but file still exists!)
http://forums.mysql.com/read.php?26,516508 (Slave has more data than Master?)
http://forums.mysql.com/read.php?26,507467 (Cannot start slave after long time of being shut down)
http://forums.mysql.com/read.php?20,504949 (Crash recovery)
http://forums.mysql.com/read.php?26,436609 (wrong hint on "Increase max_allowed_packet on master"?)
http://forums.mysql.com/read.php?26,426658 (Master Master Replikation broken Slave_IO_Running: No)
http://forums.mysql.com/read.php?26,424136 (Slave IO Stops on new binlog file)
http://forums.mysql.com/read.php?26,409870 (Got fatal error 1236)
http://forums.mysql.com/read.php?26,406512 (harddisk ran full, replication is now broken)
http://forums.mysql.com/read.php?26,390826 (Replication stopped)
http://forums.mysql.com/read.php?20,390640 (Slave_IO_Running=NO)
http://forums.mysql.com/read.php?26,389881 (Got fatal error 1236 from master when reading data from binary log)
http://forums.mysql.com/read.php?26,385475 (Transactions missing in bin logs [Solved])