Hi first time have asked ?. I found a bit of water in bottom tray , Have also sprayed coating of oil in tray ,have been getting the odd beetles.
Hi Mickle
I am going to welcome you but I can’t answer your question. Wrong continent. Wrong climate.
Stand by though, help and advice coming
Welcome to the Flow forum!
A bit more information would help. Have you had a lot of rain recently? Is the inner cover under the roof wet? Is the hive near a sprinkler or other water spray? If none of these are the case, is there a lot of good forage blooming in your area at the moment? As you probably know, when bees go out foraging and bring back nectar, it is quite dilute. They mix it with enzymes, and then dry it inside the hive by fanning their wings. If they are bringing in a lot of dilute nectar, the moisture that they evaporate off can condense inside the hive, especially if it is cooler over night or the days are very humid.
As far as beetles are concerned, almost everybody has them in Australia, except for some lucky people in West Oz, I think. You just have to manage the numbers with good hive practices.
Please ask more questions if that isn’t clear, or perhaps give us some more information so that we can help you properly. 
Yep, that’s the issue with trays, they need to be emptied every time it rains. You should probably replace that oil every week anyway as it will get grubby and it will go rancid. Small price to pay if it is catching beetles.