Loose fitting power cord.

What rubbish.  It's perfectly well known that many manufacturers stray slightly from the established standards of external size of plug and internal size of receptacle.  Others have reported the reverse problem, struggling to get a plug all the way in.  In the past I've had problems with Cardas PCs, also being a crap manufacturer, right?

Besides the electrical tape, which I've used successfully, you have also try to improvise something to support the cord near the plug.  The heavier the cord--garden hose variety--the more likely this is to happen.  I know the biggest model of Pangea causes problems.

Try plumbers Teflon tape. Easy to remove.

Try bending the male prongs gently outward on the amp with a pliers. This will increase tension on the connection with the female connector on the lead.

You could also use an IEC C13 to C14 adapter...