strange holding KLM B744 KUL

[civil]

Whilst all traffic flies as usual, a KLM B744 SCD is holding over the ocean starting at 33000 feet, and an hour later still at 16.000 feet.
Originated from Subang, no KUL. Is it burning fuel for a return ??

KLM7021 - usually a ferry flightnr...

[Albin]

KLM has heavy maintenance work done at Subang (SZB). This is most likely a testflight after the maintenance.

[civil]

KLM has heavy maintenance work done at Subang (SZB). This is most likely a testflight after the maintenance.

Thanks! Much appreciated....