Partial answer: Significant progress, not sure how to finish it off
The dots in between the squares...
These can be interpreted
There are also some other ways to extract similar arrangements of letters:
The data collected:
So what next?
Upper half (blue)
Lower half (red) Rebus:
First red square
Second red square
Fourth red Square
Fifth red Square (Solved by JS1)
Now back to the third square: (Solved by Stiv)
Conclusion (thx to M Oehm & Stiv)