We cannot know what you're doing wrong without knowing your code, sorry.

I'm making a C++ version

all basic tests pass, but random tests throw an error.

I substitute the values ​​for random tests into my IDE - everything matches

but for some reason the website gives an error

For example:
Testing for 'WHER5EAEAQ/eSBU.R*bnZR60HOlIG!Xf07C8=bz0OCT2LROYBVXjdx9W4RjKrHzEDadtwHYbcPTbF'

expected 47
actual 49

I substitute it into my IDE - answer 47