Looks likely that the buy-back of their own shares has finished. Hence the 5% drop this week?

Like almost all companies they seem to have managed to buy their own shares back way above the price they were probably worth - in this case the price has constantly fallen throughout the buy-back which started right at the top of their 5 year price (First trade announcement - Average consideration per security acquired NZ$2.2628 - now NZ$1.92).

I don't know whether they've borrowed funds to use for the buy-back or not? Anyway very rare that shareholders get value for money with buy-backs (Just look at Glencore recently!).