[BUG] FFV1 MKV error

[Selur]

According to the debug output, the Vapourynth script crashes after 252 frames.
Looking at the Vapoursynth script:

# Imports
import vapoursynth as vs
# getting Vapoursynth core
import sys
import os
core = vs.core
# Import scripts folder
scriptPath = 'C:/Program Files/Hybrid/64bit/vsscripts'
sys.path.insert(0, os.path.abspath(scriptPath))
# loading plugins
core.std.LoadPlugin(path="C:/Program Files/Hybrid/64bit/vsfilters/Support/libmvtools.dll")
core.std.LoadPlugin(path="C:/Program Files/Hybrid/64bit/vsfilters/Support/TCanny.dll")
core.std.LoadPlugin(path="C:/Program Files/Hybrid/64bit/vsfilters/SourceFilter/LSmashSource/LSMASHSource.dll")
# Import scripts
import degrain
import validate
# Source: 'C:\Users\DSIOMNAINC\Desktop\01_02_davinci (1)-001.mkv'
# Current color space: YUV420P10, bit depth: 10, resolution: 3840x2160, frame rate: 25fps, scanorder: progressive, yuv luminance scale: limited, matrix: 709, transfer: bt.709, primaries: bt.709, format: FFV1
# Loading C:\Users\DSIOMNAINC\Desktop\01_02_davinci (1)-001.mkv using LWLibavSource
clip = core.lsmas.LWLibavSource(source="C:/Users/DSIOMNAINC/Desktop/01_02_davinci (1)-001.mkv", format="YUV420P10", stream_index=0, cache=0, prefer_hw=0)
frame = clip.get_frame(0)
# setting color matrix to 709.
clip = core.std.SetFrameProps(clip, _Matrix=vs.MATRIX_BT709)
# setting color transfer (vs.TRANSFER_BT709), if it is not set.
if validate.transferIsInvalid(clip):
  clip = core.std.SetFrameProps(clip=clip, _Transfer=vs.TRANSFER_BT709)
# setting color primaries info (to vs.PRIMARIES_BT2020), if it is not set.
if validate.primariesIsInvalid(clip):
  clip = core.std.SetFrameProps(clip=clip, _Primaries=vs.PRIMARIES_BT2020)
# setting color range to TV (limited) range.
clip = core.std.SetFrameProps(clip=clip, _ColorRange=vs.RANGE_LIMITED)
# making sure frame rate is set to 25fps
clip = core.std.AssumeFPS(clip=clip, fpsnum=25, fpsden=1)
# making sure the detected scan type is set (detected: progressive)
clip = core.std.SetFrameProps(clip=clip, _FieldBased=vs.FIELD_PROGRESSIVE) # progressive
clip = core.std.Crop(clip=clip, left=0, right=0, top=190, bottom=190)# cropping to 3840x1780
# removing grain using MCDegrain
clip = degrain.mcdegrainsharp(clip=clip)
# set output frame rate to 25fps (progressive)
clip = core.std.AssumeFPS(clip=clip, fpsnum=25, fpsden=1)
# output
clip.set_output()

The script seem fine to me.
Does the Vapoursynth Preview work when scrolling through frame 250+?

Cu Selur