javascript - Chrome DevTools won't let me set breakpoints on certain lines -

in image above, tried setting breakpoints on every line line 437 line 443. however, cannot set breakpoints on lines 439 , 440. when function runs, breakpoints on lines 437, 438, 441, , 442 ignored. chrome breaks on line 443. means cannot debugging before first conditional runs.

when click on lines 439 or 440, breakpoint appears half second , jumps line 443.

is bug or missing something? how set breakpoint @ or before line 439?

if using js minification , sourcemaps, ensure date source code.