Hi @AldoNaletto and welcome to Codewars!

Which language do you notice this in? Also if you want to make a bug report please provide inputs/console logs for concrete evidence: read this troubleshooting guide - section on Print Your Input/Output

Then in your language, include a console.log() / print() / etc. command to display:

1. the value of the input and
2. the value that your solution outputs.

pseudocode example

my_function(codewars_argument):
   print_to_console(codewars_argument) <--- add this line to your code
   my_answer = 3+4+8
   print_to_console(my_answer) <--- and add this line also
   return my_answer

These values will appear in the Codewars console so you can copy paste them here in Discourse. Only then can people know if the kata is wrong or if it is your code.

The random tests are failing with big numbers, about 10 decimal digits: the verification algorithm fails and expects one more bit 1 than actually exists

That's a problem with your code not a kata issue. For some input values your numeroEnBinarioString value is null. Read this: https://docs.codewars.com/training/troubleshooting