in thingatpt.el:

;; The function bounds-of-thing-at-point finds the beginning and end
;; positions by moving first forward to the end of the "thing", and then
;; backwards to the beginning.

;;;;;;;

Also *bounds-of-thing-at-point jumps to-and-fro, doing some sanity check 
every time.

Suggest to jump ***first *at the beginning, as backward move might be slow.

Avoid to-and-fro, deliver tests instead, so first try will be reliable 
or return nil.
*