jirestre I have to move the power connector side to side to make good contact, but I see little sparks, so this is not good.
This is often caused by the use of the wrong plug. There are two standards that are very close to each other.
Both have 5.5mm barrels (the external diameter of plug). But the plugs on one has 2.1mm hole and the other has 2.5mm hole.
Check to see if the plug that you are using is a 5.5mmx2.5mm plug instead of a 5.5mmx2.1mm plug.
The 2.1mm jacks ("sockets") have a 2.1mm diameter center pin. The 2.5mm jacks have 2.5mm center pins.
A 5.5mm x 2.1mm jack lets you plug a 5.5mm x 2.5mm plug in, but the internal contact will be loose. On the other hand, a 5.5mm x2.1mm plug will be prevented from fully seating if it is plugged into a 5.5mm x 2.5mm jack.
What I do is to keep a known "reference" 2.5mm jack around, and if a plug does not go in completely, the plug is a 2.1mm type, otherwise the plug is a 2.5mm kind. Likewise, I keep a known "reference" 2.1mm plug around, and if it plugs into a jack, the jack is 2.1mm, otherwise, the jack is 2.5mm. Keep those in your toolbox, and in the future, you can very quickly test connectors.
DeepSkyDad's (the same Pavle who makes the RedCat/Camera lens gears for the ZWO EAF) USB Hub, for example, uses a 2.5mm jack for power; a 5.5/2.1 plug will not plug into it. You will also find that higher powered USB hubs use 2.5mm, because they can carry a larger current.
Chen