When I enable flycheck and (setq truncate-lines t)

sometimes  posn-at-point get strange info like the below:

        (#<window 3 on test.el> 31 (65 . 111) 0 (! . 0) 31 (5 . 3) nil (0 . 24) (13 . 29))

At the same point, the normal info is like:

       (#<window 3 on test.el> 31 (65 . 87) 0 nil 31 (5 . 3) nil (0 . 0) (13 . 29))

is the overlay's problem?