For the video I recommend using a free open source screen recording software like, ShareX for windows or Kap for Mac, then uploading it onto imgur or streamable (makes it a lot nicer for those viewing, will also attract you more help and attention)
Well you could create a region3 centered at the hit location, then use the Find Parts in Region 3 Function of workspace to find the parts needed to be destroyed.
However, it may be easier to use the rotatedregion3 Module, since you can place a sphere part at the explosion center and use that as a region 3 to find parts within it:
However, I wonder why it’s unreliable though any explanations?