Can you repeat the problem? If so, what are the steps?
Yes. Using a new Shotcut session, enable jack support. Then Open File and add a video that got audio. The audio will bypass jack totally and will blast at the loudest possible volume.
I create music. I use Yamaha powered monitors and subwoofer. LUCKILY the hardware volume on each speaker was relatively low, at about 4 for the highs and 2 for the subwoofer. So no harm was done to the equipment, I can’t imagine the blast it would have been with the Yamaha hardware audio set at 7 or more. There could have been hardware damages caused by this as far as quality of audio delivery is concerned.
This is major problem.
Apart from this, the sync between software works well. When Play is activated in Shotcut Bitwig also starts playing. It would be so cool to have Shotcut AND Bitwig working together in real time with proper audio since this would allow to make music changes at the same time the video is created. Instead, a stereo export has to be done from Bitwig, then imported into Shotcut to build the video.