If a window size change occurs while a child is executing, bash2 won't get the SIGWINCH and won't adjust its idea of the terminal size. It should use TIOCGWINSZ to check the window size (just like the SIGWINCH handler does) after anything which could have caused it to miss window size changes.
There is an option to set in bash that changes the behaviour of bash wrt SIGWINCH. Please look for checkwinsize.