Regression, 3rd stage bootup SOMETIMES requests for ctrl+alt+del, but even when pressed does not allow me to log in

a 0.4.15-dev-2534-geba00d1 gcc 8.4.0 win dbg build, on VBox4.3.12.
Self-Built using RosBE2.2.1, with a cleared output folder, reconfigured and rebuilt from scratch.

(After I suffered from CORE-17581 in 2nd stage)
The 3rd stage bootup does not bring me to desktop (as it used to do in the past), but instead it requests for ctrl+alt+del, but even when I send those keys via VM, it still does not start the shell. I can not use/test ros like this.

0.4.15-dev-2534-geba00d1_3rdStage.png
0.4.15-dev-2534-geba00d1_3rdStage.log

It appears to be a regression for me, although others seem to not suffer from that?
I have not tested ros master the last 3months, most likely it was introduced during that timeframe.

The bug is of sporadic nature, I'd estimate reproducibility to be <10% with an affected build only.

Regression test the hard facts
0.4.15-dev-2569-g9f549db_ctrl+alt+del_affected.png gcc 8.4.0 selfbuilt
reactos-bootcd-0.4.15-dev-2534-geba00d1-x86-gcc-lin-dbg.iso
reactos-bootcd-0.4.15-dev-2480-gcd085ac-x86-gcc-lin-dbg.iso
reactos-bootcd-0.4.15-dev-2330-gaea948a-x86-gcc-lin-dbg_GOTCHA_on1stTry.png
reactos-bootcd-0.4.15-dev-2320-gf3e1697-x86-gcc-lin-dbg_GOTCHA_on1stTry.png
reactos-bootcd-0.4.15-dev-2308-gb10d92a-x86-gcc-lin-dbg_GOTCHA_on1stTry.png
reactos-bootcd-0.4.15-dev-2307-g4337841-x86-gcc-lin-dbg.iso 12 x tested
reactos-bootcd-0.4.15-dev-2300-g82c9081-x86-gcc-lin-dbg.iso 10 x tested
reactos-bootcd-0.4.15-dev-2200-g8494688-x86-gcc-lin-dbg.iso 10 x tested
reactos-bootcd-0.4.15-dev-2022-g44eecfa-x86-gcc-lin-dbg.iso 10 x tested
reactos-bootcd-0.4.15-dev-1627-gaf0f858-x86-gcc-lin-dbg.iso 2 x tested