@audiocanada - Try the aluminum foil tape (Home Depot) used on heating ductwork.
A couple of small pieces on the underside of the plug should be adequate
- it is not spongy or slippery
- just make sure it does not extend past the end of the plug and touch the pins of the socket
ALSO - support the cables as stated above
It’s not really about how tight the plug housing is, but how tight the pins are gripped by the IEC socket that matters
I make my own PC’s and use Sonar Quest silver palted copper connectors, because they grip the pins like a vice.
Good power cables will generally have pretty good connectors
Hope that helps - Steve (Canada)