From the release: "The drilling of the Mukuyu-1 ST1 has...

From the release: "The drilling of the Mukuyu-1 ST1 has recommenced and the mud system is being displaced to the planned lighter weight drilling mud in preparation for drilling ahead".

The fact they're displacing from the old mud system to the lighter mud system indicates to me that they've successfully kicked off the sidetrack. When you're drilling cement plugs there will be a certain amount of cement contamination of the mud system. In this scenario if you have a programmed mud system change then you're best doing it after you've drilled the cement and are into new formation. The old cement contaminated mud is dumped and you drill ahead with clean mud.

The above procedure is also generally followed when drilling out a casing shoe and starting a new hole section.