If anyone is having problems detecting raid cooldowns for group 5/6 in raids, just edit the line of code in ExCD2.lua located in
C:\Program Files (x86)\World of Warcraft\Interface\AddOns\ExRT
In GetNumGroupMembersFix (line 3163) function change the final return value to 30 instead of n. Should fix it and hasn't borked the addon yet....
Hope this helps.
(get notepad++ if you want an easier time editing the file)