Why i have loss when coding with Convolutional code and decoding with Viterbi ?

I made a model in Simulink made from the following blocks: random integer, integer to bit converter, convolutional encoder, viterbi decoder, bit to integer converter, display. I am using an Error rate calculator block to check is what i send is what i receive. I don't understand why i always have data loss up to 50%. The percentage is related to the integer generator configuration and can be down to 30%. I don't understand why this is happening. I am missing something ? Please help me to make the loss go away.

Thank you.