Regression: 0.4.15-4871 breaks, BSOD Cygwin setup

Environment: VirtualBox 6.0 on Linux

It works fine on both XP and Server 2003.

Suspected guilty commit: https://github.com/reactos/reactos/commit/4471ee4

Description for 4871-4922:

Attempting to install Cygwin results in a 0x1E bluescreen.
Entered debugger on last-chance exception (Exception Code: 0xc0000005) (Page Fault)
Memory at 0x0000001C could not be accessed

It crashes just before postinstall scripts.

(Cygwin setup's progress percentage is a bit confusing, post-install scripts start over from 0%)

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[FIXED] Description for 3659-4860 (QUOTA_UNDERFLOW):

Fails on: reactos-bootcd-0.4.15-dev-3659-g0c07eac-x86-gcc-lin-dbg.iso to 4860-g85afdf

Works on: reactos-bootcd-0.4.15-dev-3658-gee697cf-x86-gcc-lin-dbg.iso and earlier.

Works AGAIN on: reactos-bootcd-0.4.15-dev-4861-g5da5e64-x86-gcc-lin-dbg.iso

Attempting to install Cygwin results in QUOTA_UNDERFLOW bluescreen.

Things happen quickly after "(/ntoskrnl/mm/balance.c:145) MM BALANCER: Removing access bit!" but look like normal debug messages from running Cygwin.

It crashes during postinstall scripts

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Cygwin: (See attached zip-file in CORE-18247, using `drive=C`)