Whirlpool (LGR4634EQ3)

During the dry cycle, I heard something going from lint pipe now the heat is very less, and timer runs faster than usual with out drying the clothes

Whirlpool - LGR4634EQ3
I checked thru hole in the front and can see ignite and flame come but last for 10 seconds only at time of start.
Please let me know what parts need to be replaced