Target of Target box disappears

Type of Internet Connection: Fibre Broadband
Internet Connection Speed: 36.3mb
Date & Time: 21:20 GMT 27-02-16
Frequency: Sometimes, Intermittent
World: Sargatanas
Character Name: Kalo Koko
Monster Name: Echinda (void ark)
Class/Level: sch 60
Party or Solo: Alliance 24 members
Race: lalafell
In-Game Time: as above
Area and Coordinates: Void Ark
Steps:
Fighting Echinda I noticed the target of target box had disappeared which I sometimes use to quickly target the main tank of the alliance.

then cycling my party list the target of target box didn't appear telling me anyone was targeting echidna even though they visably were.

The box came back about half way through the fight but when tested outside of voidark noticed the same problem randomly occurs, a few people in my fc noticed the same thing when testing it as I was looking through the settings thinking I had somehow disabled it.