Black Screen videos, videos shrinking into the corner and general lag are all VLC issues.
You need to change to WMP in options.
By doing this if you have any videos that aren't in standard mp4 format they won't play at all so installing a codec pack is necessary.
https://www.codecguide.com/download_k-lite_codec_pack_basic.htm
There's a volume slider in the top bar of LB if they're too loud.
@Audioout
@Retrofrogg