Unpaid levies

Hi…we have moved to strata living…lots to love about it. After being here 3 months we have learnt that 2 owners are not paying their levies. One pays a whole full year in arrears….SM says not to worry, money eventually comes in. This owner lives oversea. Unit is rented out.
The second one, more worrying has not paid for 3years…SM has told owners it is too hard to case and would cost too much in legal fees to do so. Amount owing with normal and special levies is approx $20,000. This doesn’t help the financials…
We were not made aware of these arrears when strata search was done…shouldn’t it have shown up somewhere?
The unit has been rented over the past 3 years….could we garnish the rent.?
Hopeful for advice