[RealHW] Debug log gets truncated after serial.sys is loaded

This is happening when testing reactos on an old HP Pavilion, last test on this machine was some years ago, so it's a regression, but doing a bisect is useless for me right now because I have little to no spare time to test this.

The main symptom is: debug log is truncated when loading serial.sys (I am debugging with serial null modem cable), when I see the putty log, I can notice at least 3 errors with this description:

(/ntoskrnl/mm/ARM3/sysldr.c:182) Loading: \SystemRoot\System32\drivers\serial.sys at FB053000 with 13 pages

(/ntoskrnl/io/pnpmgr/pnpres.c:641) Resource conflict: IRQ (0x4 0x4 vs. 0x4 0x4)

(/ntoskrnl/io/pnpmgr/pnpres.c:641) Resource conflict: IRQ (0x4 0x4 vs. 0x4 0x4)

My environment is: ReactOS 0.4.15-x86-dev (Build 20210628-0.4.15-dev-2802-g8a68820) (Commit 8a68820429810dd187f64d37e47ab12f7432f410)