I lowered the version from 4.2.1 to 4.1.1 and reverted to the version that has shift_tokens_right in Seq2SeqDataCollator.
I revert my own DataCollator to the old version, then, apparently, the above problem no longer occurs.
Are there any tips to make my own DataCollator for Seq2SeqTrainer in v4.2.1?
Thank you.