Cigarette lighter plugs

Tony, you answered your own question, Merrit/Hella Plugs...............

I've never had an issue with Merit plugs jumping out, but my preferred method is andersons.

To me it's horses for courses.
Where I want or need a large current draw like a compressor, then Anderson.
Where I need lower current like fridge Merit /Hella.
For small currents like battery charger I use the small red/black Andersons as they are very compact.
I do not use Anderson for link to caravan as I have seen one disconnect then be destroyed on a dirt road , which left the owner stranded with no fridge until I supplied a spare.
Supercheap do a positive locking 2 pin 50 amp plug that positively locks the same way as a trailer plug.

If you need to use a cigarette socket type plug/power connector try the LION Heady Duty Accessory Plug LA115G6 rated at 180w. Over many years I have tried several other brands of plugs for use in the boating & 4WD environment. Wiring of this plug is awkward but once assembled the 4 spring terminals provide very strong locking and work reliably with heavy loads if mated to the correct components.

Merits work OK but I have found wrapping a thin rubber band around a standard plug or putting a thin O ring around around a standard plug also works as good as a Merit.

ARB plugs and sockets are the best as they lock in but then you have to change every one you have as nothing else is common and you have to make up an adaptor for standard items you may want to use.

I’ve used the Engel screw in connectors and found them to be very good.