⁇ in predicted text
The conformer network sometimes predicts "⁇" symbols. After greedy decoding, all the outputs have zero index, which corresponds to <"unk"> token. And finally, after applying sentencepiece tokenization I am getting  ⁇ symbols. 


Btw, all my transcripts successfully tokenized without producing any <"unk"> symbols. 

What can cause "⁇"  symbol?