Hello. 
So I have a 4K movie file and I wanted to export it as a smaller file size while keeping the same video resolution. I had done this successfully previously but this time the exporting would constantly fail. I use dual pass to get a higher quality file. With these 4K files I export them without audio as I can take care of the audio afterwards. I assume that it has to be something with the movie file that is conflicting with Shotcut so here is the video info of the file to see if there is anything there that could answer why the exporting constantly keeps failing:
Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main 10@L5.1@High
Codec ID : V_MPEGH/ISO/HEVC
Duration : 2 h 28 min
Bit rate : 23.5 Mb/s
Width : 3 840 pixels
Height : 2 160 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 23.976 (24000/1001) FPS
Standard : NTSC
Color space : YUV
Chroma subsampling : 4:2:0 (Type 2)
Bit depth : 10 bits
Bits/(Pixel*Frame) : 0.118
Stream size : 24.4 GiB (68%)
Writing library : x265 2.5+6-d11482e5fedb:[Windows][GCC 7.1.0][64 bit] 10bit
Encoding settings : cpuid=1173503 / frame-threads=3 / numa-pools=8 / wpp / no-pmode / no-pme / no-psnr / no-ssim / log-level=2 / input-csp=1 / input-res=3840x2160 / interlace=0 / total-frames=172743 / level-idc=51 / high-tier=1 / uhd-bd=1 / ref=1 / no-allow-non-conformance / repeat-headers / annexb / aud / hrd / info / hash=0 / no-temporal-layers / no-open-gop / min-keyint=1 / keyint=24 / bframes=3 / b-adapt=0 / b-pyramid / bframe-bias=0 / rc-lookahead=5 / lookahead-slices=8 / scenecut=0 / no-intra-refresh / ctu=32 / min-cu-size=16 / no-rect / no-amp / max-tu-size=32 / tu-inter-depth=1 / tu-intra-depth=1 / limit-tu=0 / rdoq-level=0 / dynamic-rd=0.00 / no-ssim-rd / no-signhide / no-tskip / nr-intra=0 / nr-inter=0 / no-constrained-intra / strong-intra-smoothing / max-merge=2 / limit-refs=0 / no-limit-modes / me=0 / subme=0 / merange=57 / temporal-mvp / no-weightp / no-weightb / no-analyze-src-pics / deblock=0:0 / no-sao / no-sao-non-deblock / rd=2 / early-skip / rskip / fast-intra / no-tskip-fast / no-cu-lossless / no-b-intra / rdpenalty=0 / psy-rd=2.00 / psy-rdoq=0.00 / no-rd-refine / analysis-reuse-mode=0 / no-lossless / cbqpoffs=0 / crqpoffs=0 / rc=crf / crf=12.0 / qcomp=0.60 / qpstep=4 / stats-write=0 / stats-read=0 / vbv-maxrate=160000 / vbv-bufsize=160000 / vbv-init=0.9 / crf-max=0.0 / crf-min=0.0 / ipratio=1.40 / pbratio=1.30 / aq-mode=1 / aq-strength=0.00 / cutree / zone-count=0 / no-strict-cbr / qg-size=32 / no-rc-grain / qpmax=69 / qpmin=0 / no-const-vbv / sar=1 / overscan=1 / overscan-crop=0 / videoformat=2 / range=0 / colorprim=9 / transfer=16 / colormatrix=9 / chromaloc=1 / chromaloc-top=2 / chromaloc-bottom=2 / display-window=0 / master-display= / R: / x=0.680000 / y=0.320000, / G: / x=0.265000 / y=0.690000, / B: / x=0.150000 / y=0.060000, / White / point: / x=0.312700 / y=0.329000" / max-cll=1000,500 / min-luma=50 / max-luma=1000 / log2-max-poc-lsb=8 / vui-timing-info / vui-hrd-info / slices=1 / opt-qp-pps / opt-ref-list-length-pps / no-multi-pass-opt-rps / scenecut-bias=0.05 / no-opt-cu-delta-qp / no-aq-motion / hdr / hdr-opt / no-dhdr10-opt / analysis-reuse-level=5 / scale-factor=0 / refine-intra=0 / refine-inter=0 / refine-mv=0 / no-limit-sao / ctu-info=0
Default : Yes
Forced : No
Color range : Limited
Color primaries : BT.2020
Transfer characteristics : SMPTE ST 2084
Matrix coefficients : BT.2020 non-constant
Maximum Content Light Level : 1000 cd/m2
Maximum Frame-Average Light Le : 500 cd/m2
Thanks!