Why would spondylolysis keeps re-occurring?

Not all heal and can: Cause recurrent symptoms. This defect is seen in about 6% of people but not all have symptoms while some do and even fewer have recurrent back pain with 10% overall getting surgery for persistent symptoms that fail nonoperative care like exercise and pt, bracing, medication and activity modifications.

Treatment...: Perhaps you did not wait long enough for it to heel before resuming your regular activities. Physical therapy is usually done for 3- 6 months.