I only heard one explosion of a V 2 rocket in the Strood / Wainscot area in 1944/5 - (& the swoosh)
That one landed in Salter`s Cross area - I heard of no other - in the area.
I suggest it was an offical / unoffical explosion of unstable explosives - given the depth of the hole.
The RE museum in Brompton - the Sapper - could have the answer - talk to him ( have V 2 there )