Help/Advice Needed for Indoor Water Fountain!!

Hi!

This is my first post here.. cos I desperately need some help with my indoor water fountain. Please let me know if I am posting in the wrong forum as I couldn't find a more suitable forum.

This is probably our 4th water fountain that the vendor changed for us. But the same problem is occurring again - he came and checked, but could not find out the reason. All he said was that the water could have 'back-flowed' from the water sprout, and that I should monitor it and let him know again.

The fountain is placed indoor, on the 6th storey of an apartment, no wind at all, no external factors that could have caused this. I have removed all stones, and left some fake plants (as you can see from the picture). [Note: Even with the plants taken out, the problem still occurred..]

The fountain would be ok for some days all in a row (without leakage), and then suddenly, it would start to leak from the two areas that I have indicated in red in thepicture here. Initially I thought it was the water level, and I tried to fill the water up to a certain level, and it stopped leaking for a while. But suddenly, the leakage came back today.. and although I filled water to the same level, the leakage continued, from the two areas that I have indicated in the picture attached.

I desperately need some experts to advise me here.. . as it is driving us crazy, as the pattern of the leakage is so erratic, I failed to find the reason.

Any help or advice would be greatly appreciated! Thank you!

My water fountain picture - click here

Or here: 

https://www.flickr.com/photos/90562463@N04/27075390232/in/dateposted-public/