timeout sending a char

[bellonemauro]

Dear Developer,

thanks for this lib that I use constantly in few of my open projects.
I have written a simple function to send a specific string to a custom device

bool sendData(const string &_data) {
if (m_serial->isOpen()) {
if (m_serial->write(_data) > 0) {
return true;
}
}
return false;
}

where m_serial is a serial lib port object well initialized.
This function works always, any string I send is fine, except the #

if I send the #, it get stuck in win.cc at line 352

if (!WriteFile(fd_, data, static_cast(length), &bytes_written, NULL)) {

no debug errors, just stay there forever.
Aapplication running on windows 10, and compiled using MSVC 2015.

Do you have any clue on the possible reason?
Thanks
Mauro