Here are the file properties (from VP23 and Home Media Player). I tried opening about five different movies (1080p, BDRip and BDRemux), and it was always the same. It took 10 minutes to open a 7Gb BDRip from HDD drive. My system is definitely clean; I don't use pirated software.

from VP23

General
  Name: Brothers.mkv
  Folder: E:
  Type: Matroska Video
  Size: 7,85 GB (8 040 798 639 bytes)
  Created: 8 february 2026 y., 18:02:01
  Modified: 8 february 2026 y., 18:03:16
  Accessed: 8 february 2026 y., 18:04:44
  Attributes: Archive

Media information
  Stream format: Matroska
  Video stream #1
    Video format: AVC
    Resolution: 1920 x 1080 px
    Aspect ratio: 16:9
    Color depth: 8 bit
    Frame rate: 23.976 fps
    Scan type: Progressive
    Bit rate: 9614000 bps
  Audio stream #1
    Audio format: AC-3
    Sampling rate: 48000 Hz
    Channels: 6 channels
    Bit rate mode: Constant
    Bit rate: 640000 bps

Streams
  Video: 01:44:37,938, 23,976 fps progressive, 1920x1080x32, AVC
  Audio: 01:44:37,760, 48000 Hz, 16 Bits, 6 Channels, AC-3

ACID information
  ACID chunk: no
  Stretch chunk: no
  Stretch list: no
  Stretch info2: no
  Beat markers: no
  Detected beats: no

Other metadata
  Regions/markers: no
  Command markers: no

Media manager
  Media tags: no

Plug-In
  Name: mxcompoundplug.dll
  Folder: E:\SteamLibrary\steamapps\common\VEGAS Pro 23 Steam Edition\App\FileIO Plug-Ins\mxcompoundplug
  Format: MAGIX MKV
  Version: Version 23.0 (Build 302)
  Company: MAGIX Computer Products Intl. Co.

from Home Media Player

General
Unique ID                      : 134268547778002847245390632315335405332 (0x65032E82492DDBACFADCD8F3416EEF14)
Complete name                  : E:\Brothers.mkv
Format                         : Matroska
Format version                 : Version 4
File size                      : 7.49 GiB
Duration                       : 1 h 44 min
Overall bit rate               : 10.2 Mb/s
Encoded date                   : UTC 2026-02-08 15:02:01
Writing application            : mkvmerge v56.1.0 ('My Friend') 64-bit
Writing library                : libebml v1.4.2 + libmatroska v1.6.4

Video
ID                             : 1
Format                         : AVC
Format/Info                    : Advanced Video Codec
Format profile                 : High@L4.1
Format settings                : CABAC / 4 Ref Frames
Format settings, CABAC         : Yes
Format settings, Reference fra : 4 frames
Codec ID                       : V_MPEG4/ISO/AVC
Duration                       : 1 h 44 min
Bit rate                       : 9 614 kb/s
Width                          : 1 920 pixels
Height                         : 1 080 pixels
Display aspect ratio           : 16:9
Frame rate mode                : Constant
Frame rate                     : 23.976 (24000/1001) FPS
Color space                    : YUV
Chroma subsampling             : 4:2:0
Bit depth                      : 8 bits
Scan type                      : Progressive
Bits/(Pixel*Frame)             : 0.193
Stream size                    : 7.02 GiB (94%)
Writing library                : x264 core 159 r2991 1771b55
Encoding settings              : cabac=1 / ref=4 / deblock=1:-3:-3 / analyse=0x3:0x113 / me=umh / subme=11 / psy=1 / psy_rd=1.05:0.00 / mixed_ref=1 / me_range=32 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-2 / threads=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=0 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=9 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=240 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=2pass / mbtree=0 / bitrate=9614 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=50000 / vbv_bufsize=62500 / nal_hrd=none / filler=0 / ip_ratio=1.40 / pb_ratio=1.30 / aq=3:0.80
Language                       : English
Default                        : Yes
Forced                         : No
Color range                    : Limited
Color primaries                : BT.709
Transfer characteristics       : BT.709
Matrix coefficients            : BT.709

Audio
ID                             : 2
Format                         : AC-3
Format/Info                    : Audio Coding 3
Commercial name                : Dolby Digital
Codec ID                       : A_AC3
Duration                       : 1 h 44 min
Bit rate mode                  : Constant
Bit rate                       : 640 kb/s
Channel(s)                     : 6 channels
Channel layout                 : L R C LFE Ls Rs
Sampling rate                  : 48.0 kHz
Frame rate                     : 31.250 FPS (1536 SPF)
Compression mode               : Lossy
Stream size                    : 479 MiB (6%)
Language                       : English
Service kind                   : Complete Main
Default                        : No
Forced                         : No

@BlackOps Note that in the update log of VP23B356, there's such a fix:

• Fixed a crash which may occur when reading some AVC media

I'm not sure if your media is also within the affected range.

Since VP23B356 is a withdrawn build, we can no longer get its installer. The one I installed is also VP23B302, but other users on the forum might still be using VP23B356. You can send a sample media file through another file hosting service like Google Drive and ask users using VP23B356 to test it to see if it still causes freezing.

Still, it has to be said that Magix seems to have been rather negligent regarding VP23. Since VP23B356 was withdrawn, Magix has not provided an official response, as if it had vanished...

Not sure if Dolby audio support is still in Vegas due to proprietary licensing. MKV may also be an issue. A more plain vanilla approach may be converting the audio to 6-channel mono wav in a mov container. Or 6-channel aac in an mp4 container... I think there was a thread about that a while back but don't recall it succeeding.

I am guessing that currently 5.1 AC3 in an MKV file is not properly working. I would suggest transcoding it to an MP4.