x265 Encoding Issue with MP4Box

[Selur]

Since you do not want to share details that would help me to reproduce and fix the issue my only recommendation is to tell Hybrid not to use MP4Box but FFmpeg for .mp4 muxing by enabling "Config->Output->Container Settings->Mp4 Settings->FFmpeg instead of MP4Box".
Ah correction you did provide a debug output (appeared after I posted).
Mp4Box aborts with:

system failure for file opening of 2019.11.03.1 -tmp C:\Users\Admin\AppData\Local\Temp -new C:\Users\Admin\Desktop\19_35_13_1010__03.mp4 in mode w+b: 0x0000007b
Error: I/O Error

    Error: I/O Error

-> is your drive full? Orare there some problems with the access rights or some over protective anti virus?

Cu Selur