Help with v3 problems
You might be better off just switching to v4 if you can, everything should "just work" as long as your GPU is capable, but here are some common workarounds for Microsoft DirectShow problems that tend to plague v3 users.
Problems with the LAV Video Decoder
Sometimes LAV Video Decoder has an error because it didn't recognise some video data.
If the error happens only occasionally on a channel that usually works, it'll be because of a signal glitch. Retuning or fixing your antenna may help.
If the error happens always make sure your LAV Video Configuration app (from your Windows Start menu) has the MPEG2, H.264 and H.265 options ticked under its Formats tab.
You could also try making sure you're running the latest version from github.com/Nevcairiel/LAVFilters.
Problems with the LAV Audio Decoder
Sometimes LAV Audio Decoder has an error because it didn't have an audio type enabled.
Make sure your LAV Audio Configuration app (from your Windows Start menu) has the AAC, AC3, EAC3 and MP2 options ticked under its Formats tab.
If they are and it still doesn't work you could also try making sure you're running the latest version from github.com/Nevcairiel/LAVFilters.
When codecs complain of 'No Hardware'
Simply plugging in the speaker cable should fix it.
This usually only happens with some audio decoders like the 'Microsoft DTV-DVD Audio Decoder'. What it means is the decoder couldn't find speaker output hardware, which most of the time is because your Windows speaker selection is set to something like 'Headphones' or 'Speakers (High Definition Audio Device)' but no headset or speaker cable is plugged into the jack, which on some computers makes the audio device completely 'disabled'.