AviSynth+ Doubling the video lenght?

The only slightly odd thing I see is the fpsnum=0 setting when you open the video. I'm not sure what that does. If you put the output video into MediaInfo, what fps does it report? Is everything playing in slow motion? Or, is it playing at normal speed and the video repeats twice? What application are you using to read the AVISynth script, and how does that application save the video? That may be where the problem is.

mediainfo sees your file which has been encoded 2 days ago as MPEG-4AVC in VFR with AAC, no Largarith nor MagicYUV. Is that your source ? A sample of the source would be helpful. What happens if you try LWLibavVideoSource and reduce the script to only Code:

If VHS capturing: There are lots of guides here. I suggest to take the source VHS tape framerate as-is, matching the settings of capturing device to the source video system. If you force non-matching settings, you will capture wrong. If Brazil, then extra consideration. I remember Brazil using the hybrid PAL-M (PAL color carrier, but NTSC frame properties) so I am expecting 29.97i fps (525 timing lines, 480 picture lines). Level were different too, I remeber to have seen elevated black pedestal and white at lower levels. If capture device has no setting "PAL-M" then you would capture in setting "NTSC", and correct levels later in Avisynth. If the result is for archival and to be kept interlaced, encode as 4:2:2 and you are done. If the result is for playback on progressive OLED/LCD screens: You may want to use QTGMC. This gives your desired 59.94 fps progressive frames, these you may encode as you wish.