Medra DOI registration error

I have a problem when I register in Medra articles that have references. What format do references follow? Is there a problem with the plugin?

OJS 3.3.0-14

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘minLength’] The value ‘_ref1’ has a length of ‘5’; this underruns the allowed minimum length of ‘11’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘pattern’] The value ‘_ref1’ is not accepted by the pattern ‘10.\d*/\S*_ref\d+’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘minLength’] The value ‘_ref2’ has a length of ‘5’; this underruns the allowed minimum length of ‘11’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘pattern’] The value ‘_ref2’ is not accepted by the pattern ‘10.\d*/\S*_ref\d+’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘minLength’] The value ‘_ref3’ has a length of ‘5’; this underruns the allowed minimum length of ‘11’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘pattern’] The value ‘_ref3’ is not accepted by the pattern ‘10.\d*/\S*_ref\d+’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘minLength’] The value ‘_ref4’ has a length of ‘5’; this underruns the allowed minimum length of ‘11’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘pattern’] The value ‘_ref4’ is not accepted by the pattern ‘10.\d*/\S*_ref\d+’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘minLength’] The value ‘_ref5’ has a length of ‘5’; this underruns the allowed minimum length of ‘11’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘pattern’] The value ‘_ref5’ is not accepted by the pattern ‘10.\d*/\S*_ref\d+’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘minLength’] The value ‘_ref6’ has a length of ‘5’; this underruns the allowed minimum length of ‘11’.

Element ‘{http://www.medra.org/DOIMetadata/2.0/Citations}ArticleCitation’, attribute ‘key’: [facet ‘pattern’] The value ‘_ref6’ is not accepted by the pattern ‘10.\d*/\S*_ref\d+’.