When page contains more than one form that bug appears. For example when you have form A initially filled with any data and you submit form B with invalid data errors at form B become marked. Form A is filled with "old" data, but old() function returns only old data for form B. As result form A that should remain untouched become empty.
When page contains more than one form that bug appears. For example when you have form A initially filled with any data and you submit form B with invalid data errors at form B become marked. Form A is filled with "old" data, but old() function returns only old data for form B. As result form A that should remain untouched become empty.