Hi there and welcome to the forum!
If you get the neck relief dialed in and set the action at the saddles, the saddles won't move again (because they are under string tension). Any change to your setup can only therefore be due to changes in neck relief. A simple truss rod adjustment is the appropriate way to return to your setup. You can easily and safely do that yourself. With a capo and feeler gauges you can measure the neck relief when you setup and then check it when you think it's out of whack to see how much it changes. Start to keep track of that now.
If this is becomes a warranty repair or replacement case, it'll be good to have that data. Email the dealer you bought form and inform them of the situation and ask their advice. Tell them you'll start keeping track too. If the problem doesn't improve and you just have one of those rare unstable necks, the history of correspondence between you will help everyone.
If neck changes frequently and unexpectedly and doesn't settle down within the first year, I would talk to the dealer and do something about it. If I understand correctly Australia has no fixed statutory warranty period, but clear defects in materials or manufacturing are just dealt with when they need to be, right? If not, and you have a shorter fixed period of time, make sure you know about it now so you can act in time.
Warranty neck replacements can happen but they are rare, so odds are it'll probably be fine.
