Creating timelapse with ffmpeg creates artifacts in image

Question

I've been trying to create (night-)timelapses with my GoPro and putting the images together afterwards with ffmpeg, but I can't see to find a good setting. All of my tries end up with some sort of artifacts.

The ffmpeg-command:

ffmpeg -r 100 -pattern_type glob -i '*.JPG' -vcodec libx264 -crf 18 -pix_fmt yuv420p -preset veryfast  timelapse18.mp4

I've also tried slow, and different -crf. High number (lower quality) creates less artifacts, but also worse image.

Se image below for example:

EDIT: Full logg

$ ffmpeg -r 100 -pattern_type glob -i '*.JPG' -vcodec libx264 -crf 18 -pix_fmt yuv420p -preset veryfast  timelapse18.mp4
ffmpeg version 4.2.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple clang version 11.0.0 (clang-1100.0.33.8)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.1_2 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.jdk/Contents/Home/include/darwin -fno-stack-check' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, image2, from '*.JPG':
  Duration: 00:04:32.20, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: mjpeg (Baseline), yuvj422p(pc, bt470bg/unknown/unknown), 4000x3000, 25 fps, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[swscaler @ 0x1104c3000] deprecated pixel format used, make sure you did set range correctly
[libx264 @ 0x7f8f62002a00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7f8f62002a00] profile High, level 6.1
[libx264 @ 0x7f8f62002a00] 264 - core 155 r2917 0a84d98 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.videolan.org/x264.html - options: cabac=1 ref=1 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=2 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 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=1 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=10 rc=crf mbtree=1 crf=18.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'timelapse18.mp4':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 4000x3000, q=-1--1, 100 fps, 12800 tbn, 100 tbc
    Metadata:
      encoder         : Lavc58.54.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame= 6808 fps=6.2 q=-1.0 Lsize= 1018519kB time=00:01:08.05 bitrate=122611.3kbits/s dup=3 drop=0 speed=0.0616x
video:1018436kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.008126%
[libx264 @ 0x7f8f62002a00] frame I:29    Avg QP:19.68  size:529355
[libx264 @ 0x7f8f62002a00] frame P:2320  Avg QP:22.51  size:196487
[libx264 @ 0x7f8f62002a00] frame B:4459  Avg QP:23.38  size:128207
[libx264 @ 0x7f8f62002a00] consecutive B-frames: 12.5%  0.4%  0.6% 86.5%
[libx264 @ 0x7f8f62002a00] mb I  I16..4: 32.3% 56.5% 11.1%
[libx264 @ 0x7f8f62002a00] mb P  I16..4: 31.0% 37.4%  0.1%  P16..4: 10.2%  2.4%  1.9%  0.0%  0.0%    skip:17.1%
[libx264 @ 0x7f8f62002a00] mb B  I16..4: 14.3% 22.3%  0.0%  B16..8: 12.1%  2.6%  0.1%  direct:14.6%  skip:34.1%  L0:43.4% L1:49.7% BI: 6.9%
[libx264 @ 0x7f8f62002a00] 8x8 transform intra:57.8% inter:34.6%
[libx264 @ 0x7f8f62002a00] coded y,uvDC,uvAC intra: 38.0% 9.4% 0.0% inter: 14.4% 13.5% 0.0%
[libx264 @ 0x7f8f62002a00] i16 v,h,dc,p: 35% 21% 39%  6%
[libx264 @ 0x7f8f62002a00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 13% 13% 52%  4%  4%  4%  4%  3%  3%
[libx264 @ 0x7f8f62002a00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 16% 12% 16%  7% 15% 11% 10%  6%  8%
[libx264 @ 0x7f8f62002a00] i8c dc,h,v,p: 76% 12% 12%  0%
[libx264 @ 0x7f8f62002a00] Weighted P-Frames: Y:18.3% UV:4.1%
[libx264 @ 0x7f8f62002a00] kb/s:122547.38

Answer 1

Simplify the command, to eliminate the artifacts, and only after that try reintroducing some options.

Omit -crf, -pix_fmt, and -preset.

Use a more common rate, like -r 30.

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Or, if you're desperate, use a different encoder:
cat *.JPG | ffmpeg -f image2pipe -framerate 30 -c:v mjpeg -i - out.mov