Borax "Helps" and in my experience it does a great job. Certainly better than all the algecides I've dumped dollars into in the past. I dont need to keep insane levels of chlorine anymore since 50ppm borax.

But thats all it does. Helps.
Chlorine, proper PH and CYA levels are what does the heavy lifting and if you don't have those stable at least twice a day all the borax in the world isnt going to keep the algae away.

My advice is to add the borax to 50ppm and get your Chlorine much much higher and KEEP it there till the algae goes away.
After that my guess is that your current chlorine levels and borax will prevent the problem from recurring.