Regression, bootcd's usetup can not be reached anymore in Bochs 2.6.2

I used
https://sourceforge.net/projects/bochs/files/bochs/2.6.2/Bochs-2.6.2.exe/download

reactos-bootcd-0.4.16-dev-125-g798ea90-x86-gcc-lin-dbg.iso the screen remains black after the bootmenu for more than 20 minutes of waiting. It will never launch the usetup successfully. It just sits there with a black screen.
release/0.4.15/0.4.15-5-g7791a36 bootcd x86 RosBEWin2.2.2 GCC8.4.0 affected, black screen before entering usetup
0.4.14-release-125-g5b02d38 bootcd x86 RosBEWin2.1.6 GCC4.7.2 can successfully launch the usetup, complete the 1st and 2nd stage setup, hangs then endlessly when shutting down the 2nd stage setup with rotating progress-bar (== no assert)

reactos-bootcd-0.4.15-dev-1-gd328584-x86-gcc-lin-dbg.iso affected, black screen before entering usetup
reactos-bootcd-0.4.14-dev-1-gd055c9f-x86-gcc-lin-dbg.iso affected, black screen before entering usetup, I waited ~5mins
reactos-bootcd-0.4.7-dev-545-gd788a52-x86-gcc-lin-dbg.iso comes a bit further, it already displays the blue usetup background But hangs then as well reactos-bootcd-0.4.7-dev-545-gd788a52-x86-gcc-lin-dbg_almostIntoUsetup.bmp
SVN_r56111_successfullyCompleted1stStageSetup_ButFailedToBoot2ndStageSetup.PNG

Here is my rosbochs.bxrc that I used for those tests.
I have not yet found out how to make Bochs output any debuglog. Therefore none is attached.

-> Might be a regression, but the bisect result is very confusing, I deduce, that it is a bug that I worked around in the releases/0.4.14 already, or that it has a random component, or that the Bochs 2.6.2 is not working reliable. I guess it is time to find out how to collect the logs, or to test with a more recent Bochs version.

I spotted this bug when I wanted to retest CORE-6773 with master head.