Missing attributes in LimeSurvey database after successful authentication

In two of the major data collection events we have participants in the participant list that have all their attributes missing (sex, month, year, classmates, etc. ) the only things that are there in the "participant_id" (e.g. the short id) and the "access_code". For the rest of the entry in the participant table there are no values, except for the classmates column which has a value "null".

It seems that authentication was successful and on the client side, the participant had access to the designation groups data because for some of these participants we have recorded peer nomination questions in the responses table.