Are you doing it with foils, film or leaving it out? Bleach will dry up and stop processing. I free hand my balayage then use foil on each section to allow the bleach to do its thing, i use 6% mainly unless I’ve taken my time on the back and need the front to lift the same time
Are you using a bleach specifically for freehand techniques? Such as clay bleach or cream bleach?
These are designed to process out in the open, and also do not swell as much as regular bleach, which helps stop the patches
If you’re using L’Oréal multi techniques then secure your balayage pieces in foil, are you leaving it on for the right development time 50mins, and have you measured your bleach + developer+smartbond (if you’re using it) properly. If you’re using L’Oréal freehand you can’t secure this In foil but you could use pieces of foil to separate your sections.