500 Internal Server Error

Technical details:
Error: undefined function - PROJ_plaintext_to_html
***  in function "PROJ_event_get_full_data"
***  line: {L4} = PROJ_plaintext_to_html({L4})
***  call: PROJ_event_get_full_data ([ix_recmon_record])
***  call: PROJ_get_full_data ([ix_recmon_record])