Serial port hangs windows 7 at startup

[TheLocksmith]

Hi, have been using virtualbox now for a while and ran in to a problem when updating to 6.x.

I have a windows 7 guest on an Ubuntu 16.04 host.
The guest have a lot of old machines attached to it.
So I need 2 serial to usb (working) and one serial to serial (not working.
In 5.x the serial port functioned perfectly but now in 6.x the guest hangs before windows has fully loaded.
If I disable the serial port in the guest before startup the guest starts properly.
Any thoughts on what I am missing?

[socratis]

These kinds of problems that are reproducible, should be reported to the bug tracker. Either search for an appropriate bug, or open a new bug report where you'll attach your logs and other vital information. It would also help if you can post the bug report number here so other can see the progress, add information, or see the final resolution.

Truth of the matter is that the serial ports part was re-written from the ground up for 6.x, and this might be creating some problems.