modbus examples in Qt 5.12.4 working but in Qt 5.12.5 not working

"Modbus Master example" and "Modbus Slave example" in serial port not working.

monitoring serial port but only first time send requst.

windows 7 64bit 

MinGW 32bit

qt 5.12.4 : working

qt 5.12.5 : not working

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update:

find :

https://code.qt.io/cgit/qt/qtserialport.git/commit/src/serialport/qwinoverlappedionotifier.cpp?h=5.12.5&id=85ee2c658a45d2958a54045951d236769640337f

write function in QSerialPort Qt 5.12.4 without waitForBytesWritten, write data but in Qt 5.12.5 dont write data.

in file qmodbusrtuserialmaster_p.h ( https://code.qt.io/cgit/qt/qtserialbus.git/tree/src/serialbus/qmodbusrtuserialmaster_p.h?h=5.12.5 )after line 308 must be write

m_serialPort->waitForBytesWriten();