Strata levy Arrears

We have just discovered that 2 units in our block of 12 are more than $5000 each in arrears with their strata levies. The bulk of the debt for each unit is in excess of 120 days, and appears to be in the vicinity of 3 years in arrears, as our levies are just over $400 per quarter. There is an issue with our strata managers who tend to brush a lot of things under the carpet and can be a bit standoverish when questioned.
We have also found that one of the owners whose levies are in arrears is the contracted mowing/gardening person for the complex (he doesn’t live there) and it seems he is being paid well in excess of what one would normally expect for someone to mow and area of approx. 50-60 sq meters ($200 – $400 per mow !!).
My question is ‘what can we do about the arrears’? Is it possible to lodge a caveat on a property that has excessive arrears? Is there any action we can take against the strata management company if they cannot prove they have addressed the arrears situation?
Any guidance would be greatly appreciated.
Thank you.