I use this version as it is a bit smaller:
Just don't connect 3v to the 3v pin as it is an output not an input.
The relay is connected to the same USB port 5v, so that may also be the problem, and when I move the dupont cables connected to I2C, the screen turns on, off, and flicker, like the wires are no bueno.
May this be the issue?
Relay?
you hand't mentioned a relay. Relays can introduce several problems from back emf from the coil, to voltage issues from loads.
What are you turning on/off?
Can you show us full schematic of everything and post a few photos?
If you are seeing issues moving wires, then it is very possible that the wires are not making as good of contact as they should be which could cause issues.
It may not be wires, but just the connections.
--- bill