I'm starting a beautiful project for my fish-tank where I want to program some light transitions of RGB stripes with a DS3231 RTC and an LCD to monitor the whole thing

When I test the LCD it's ok but when I add the RGB-led component (with the "tick" included in an interrupt) then the LCD is completely scrambled !
Simulation run's fine.
I tested on FC5 and it works. Am I doing something wrong or is there a problem in one of the two components ?
I added my test code.