*.aac was not created!

[Selur]

Don't see any direct problem.
Does calling:

"C:\Program Files\Hybrid\64bit\ffmpeg.exe" -y -threads 12 -nostdin -i "C:\Windows\Temp\iId_5_aid_0_DELAY_-53ms_2021-01-10@23_06_59_6010_01.aac" -ac 6 -ar 48000 -acodec pcm_s16le -f wav NUL

show any errors?
If not does calling:

"C:\Program Files\Hybrid\64bit\ffmpeg.exe" -y -threads 12 -loglevel fatal -nostdin -i "C:\Windows\Temp\iId_5_aid_0_DELAY_-53ms_2021-01-10@23_06_59_6010_01.aac" -ac 6 -ar 48000 -acodec pcm_s16le -f wav - | "C:\Program Files (x86)\NeroAACCodec\win32\neroAacEnc.exe"  -q 0.75 -lc -ignorelength -if - -of "C:\Windows\Temp\iId_5_aid_0_2021-01-10@23_06_59_6010_02.aac"

show any errors?

Using:

ffmpeg -y -threads 8 -loglevel fatal -nostdin -i "E:\Temp\iId_3_aid_1_DELAY_-53ms_2021-01-10@20_48_29_7910_01.ac3" -ac 6 -ar 48000 -acodec pcm_s16le -f wav - | neroAacEnc  -q 0.75 -lc -ignorelength -if - -of "E:\Temp\iId_3_aid_1_DELAY_-53ms_2021-01-10@20_48_29_7910_02.aac"

works fine here, my guess is that it's a problem with the decoding of the source.

Cu Selur

Ps.: Only real difference that is I see is that you are using the Windows/Temp-folder.