Qt Creator crashes after pressing "Design" button.

Hello,

I am a Qt 4.9.2 user and I am using MVSC 2017 compiler to build a QML project. When I jump into Design tab on any project, Qt crashes immediately and stops working. When I debug Qt with Visual Studio, I get a "Qt5Gui.pdb not loaded " error, although I can see the Qt5Gui.pdb in C:\Qt\5.12.3\msvc2017_64 folder. When I browse and show the Qt5Gui.pdb file, I get another error "A matching symbol file was not found in this folder". I was able to reach Design tab and use the functionality before, I don't understand what happened. I also get "Unhandled exception at 0x57CDB11B (Qt5Gui.dll) in qtcreator.exe: 0xC0000005: Access violation reading location 0x00000000" error. It crashes with every program, even I create a new one. I'd appreciate any help, thanks.