Error storing spans with ner.mark

@erikwiffin Thanks a lot for sharing the output – will investigate this!

Btw, good news: We’ll likely kill the ner.mark recipe and boundaries interface in favour of a better and more flexible recipe and interface that lets the annotator select tokens by highlighting them, add multiple spans per task and also pick the label. Check out this thread for more details and a little interactive demo of how this will work :blush: