OLED display brightness and wiring issues


I'm having unstable brightness on my OLED screen and I couldnt figure out why.

I have a chinese made 128x64 Oled display that I run with software SPI. I'm using https://github.com/greiman/SSD1306Ascii library.

I have a system setup with multiple sensors that use i2c and a lot of relays.

What are the general practices for these displays? There are lots of tutorials as individual but not much on how these displays perform with a multiple sensor setup like mine. And I'm having a lot of issues.

For example I had an issue of display not running at all most of the time and after connecting Ground wire of the display to an individual GND pin on arduino that seems to be gone.

My main issue now is with the brightness of these displays. When I run i2c sensors and the display all together 7 out of 10 times I have an issue with the brightness of the OLED screen being too dark. 2 out of 10 it works fine. And 1 out of 10 the display is off the screen or flickering.

This happens mostly on external power using 12v 2a adaptor.

Is this something related to the library that someone can help with?