I had the same issue after my macbook fell from the table: flickering pixels and sometimes flashes.[br]
I fixed it easily, maybe this will be helpful for somebody:
# Open the backplate
# Check for the loose connectors
# Gently push in connectors with a plastic tool.
# In my case some connector just got loose after the hit. I guess it was the main display cable connector near the charging port[br]
# Wish you all luck :)