I've found that RC connector quality varies a great deal.
This is brand to brand and even within the same type of connectors, same brand!
Interchangability can be an issue as well.
As an e example, some HXT's can and routinely do handle 90 amps without heating or melting.
But also, some can't.
Good contact on a wide area on any connector is essential.
Good soldering technique is very important too.
Connector ends must mate tightly to have as low electrical resistance as possible and be resistant to being pulled apart for best results.
Just my experience,