Coralife 10k 18"T8 bulb

[veni vidi vici]

Just picked up 10k coralife 18"T8 and its flickering.its not the fixture because i changed bulbs and the other works fine.Does it need a break in period or is it a bad bulb?
TIA

 

[milkman]

Is the bulb connected properly (good tight connection)?
Are the caps clean?
All I could think of.