The output from the StringTable cleaning is missing the GC ID prefix:
[4.591s][debug][gc,phases,start ] GC(7) Parallel Unloading (4.591s)
[4.596s][info ][gc,stringtable ] Cleaned string and symbol table, strings: 5899 processed, 0 removed, symbols: 34149 processed, 0 removed
[4.596s][debug][gc,phases ] GC(7) Parallel Unloading (4.591s, 4.596s) 4.902ms
[4.596s][info ][gc ] GC(7) Pause Remark 70M->70M(20480M) (4.578s, 4.596s) 18.161ms
[4.591s][debug][gc,phases,start ] GC(7) Parallel Unloading (4.591s)
[4.596s][info ][gc,stringtable ] Cleaned string and symbol table, strings: 5899 processed, 0 removed, symbols: 34149 processed, 0 removed
[4.596s][debug][gc,phases ] GC(7) Parallel Unloading (4.591s, 4.596s) 4.902ms
[4.596s][info ][gc ] GC(7) Pause Remark 70M->70M(20480M) (4.578s, 4.596s) 18.161ms