Why did Thala avoided kissing Trisha?

For a scene in Ajith's Mangaaththaa, Thala has to kiss Trisha in her lips, but Ajith skipped it. Why did Thala avoided kissing Trisha, even though Trisha was ready for the same?
Ajith came almost near to the lips of Trisha, but shocking entire team of Mangaththaa he skipped kissing, making the unit members and Trisha vexed.

While Mangaththa is the 50th movie for Ajith, it is 40th for Trisha.