Problema al sincronizar Audios en pelicula 3D

Buenas, soy nuevo en el foro, no se si esta pregunta va aqui concretamente, disculpen si no es el lugar correcto.

Mi problema es que tengo una pelicula en 3D con audio en ingles y le quiero insertar el audio de la version 2D en castellano.
Al hacerlo, el audio se desincroniza conforme avanza la pelicula cada vez mas.

Dispongo de DVDfab12, MKVtoolnix y MEgui. Si necesito otro programa, avisen por favor.

El video donde quiero poner el audio es este:

MediaInfo report of "The.Lord.of.the.Rings.The.Fellowship.of.the.Ring. 3D._2001_.Half-SBS.1080p.x264.AC3.ENG-JFC..mkv" :

General
Unique ID : 63679915385363991389150256142022487377 (0x2FE84E3B1FEE5B9793738A655DE62D51)
Complete name : The.Lord.of.the.Rings.The.Fellowship.of.the.Ring.3 D._2001_.Half-SBS.1080p.x264.AC3.ENG-JFC..mkv
Format : Matroska
Format version : Version 4
File size : 10.5 GiB
Duration : 3 h 48 min
Overall bit rate : 6 601 kb/s
Frame rate : 24.000 FPS
Movie name : The.Lord.of.the.Rings.The.Fellowship.of.the.Ring.3 D
Encoded date : 2023-01-23 04:32:03 UTC
Writing application : mkvmerge v64.0.0 ('Willows') 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
Format settings : CABAC / 4 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 4 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 3 h 48 min
Bit rate : 6 151 kb/s
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 24.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.124
Stream size : 9.81 GiB (93%)
Writing library : x264 core 164 r3099 e067ab0
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=12 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=24 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=18.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
Default : No
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
Format settings : Dolby Surround EX
Codec ID : A_AC3
Duration : 3 h 48 min
Bit rate mode : Constant
Bit rate : 448 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 : 732 MiB (7%)
Title : DD 5.1
Language : English
Service kind : Complete Main
Default : No
Forced : No


Y el video donde tengo el audio en castellano es este:

MediaInfo report of "El.senor.de.los.anillos-La.comunidad.del.anillo.2001.mhd.1080p.esp.ing.ac3 .subs.mkv" :

General
Unique ID : 226422170392388180546910057125107173709 (0xAA5752E4C3F9A968F58C7803831B894D)
Complete name : El.senor.de.los.anillos-La.comunidad.del.anillo.2001.mhd.1080p.esp.ing.ac3 .subs.mkv
Format : Matroska
Format version : Version 4
File size : 7.01 GiB
Duration : 3 h 47 min
Overall bit rate : 4 401 kb/s
Frame rate : 24.000 FPS
Encoded date : 2017-09-04 14:03:34 UTC
Writing application : mkvmerge v15.0.0 ('Duel with the Devil') 64-bit
Writing library : libebml v1.3.5 + libmatroska v1.4.5

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4
Format settings : CABAC / 4 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 4 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 3 h 47 min
Bit rate : 3 500 kb/s
Width : 1 920 pixels
Height : 800 pixels
Display aspect ratio : 2.40:1
Frame rate mode : Constant
Frame rate : 24.000 FPS
Original 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) : 0.095
Stream size : 5.58 GiB (80%)
Writing library : x264 core 115 r1995 c1e60b9
Encoding settings : cabac=1 / ref=4 / deblock=1:0:0 / analyse=0x3:0x113 / me=umh / subme=8 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=9 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=2pass / mbtree=1 / bitrate=3500 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / aq=1:1.00
Language : Spanish
Default : Yes
Forced : No

Audio #1
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Commercial name : Dolby Digital
Codec ID : A_AC3
Duration : 3 h 47 min
Bit rate mode : Constant
Bit rate : 448 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 : 730 MiB (10%)
Language : Spanish
Service kind : Complete Main
Default : Yes
Forced : No


Soy bastante novato, pero veo que tienen el mismo frame rate y no se porque desincroniza. En mi ignorancia, he recortado la pelicula original y la he dejado en 3h 47min (es mas larga la parte negra del final) y nada.

Mil gracias desde ya.