Alphabet cannot encode transcript

Hey,
I was trying to train my own model with English data set .
(50 GB from common voice)
but after first epoch I’ve got following error:

Alphabet cannot encode transcript “” while processing sample “…/DataBase/en/clips/common_voice_en_1655Preformatted text6180.wav”, check that your alphabet contains all characters in the training corpus. Missing characters are: [].

does anybody knows why it happened?

Care to follow the basic guidelines before reaching out to support and expose more precisely what " I was trying to train my own model with English data set ." stands for?

I downloaded 50GB dataBase from common voice and I was trying to train it with this guid but i’ve got the error that i mentioned in first comment.

The import script is not perfect, follow the guidelines and search before you post: