Grohe Single-handle intermittent leak

Hello,

I have 3 Grohe bathroom faucets (on 2nd floor) at home and only 2 faucets leak. Installed in 2006 and only leaked recently.
- Intermittent: sometimes no leak, sometimes I found water on the Living Room floor on the 1st floor.
- Crawled underneath and saw a few drops of water underneath.
- Placed a 1-gallon bucket, sometimes bone dry and sometimes the next day is full of 1 gallon of water. But when looking up, NO Active Leak!
The problem with this leak is that: It is intermittent so I cannot locate the leak.
- Spoke to Grohe America and they sent me some repair parts (they say cartridge leak is more common than O-ring/hose leak), but just wondering if anyone here has similar issues and can advise me.

Model: Grohe Single-Handle Faucet 33413. Detail is here:
http://www.groheamerica.com/lib/1/tpi/1288812.pdf

Some items:
1. Conenction at supply: bone dry no leak.

2. Base of Faucet, supply lines x2: ? maybe O-ring leak.

3. Cartridge: ? Maybe leaking from here.

Could it be leaking when the faucet is opened?

I called Grohe and they say water pressure should be 72.5 psi or less, otherwise it can leak.
No other faucets in the house leaks, only Grohe!!!

Anyway, they already sent me the cartridge and I will replace it and report back.

Turned out the Grohe people were correct.
I tested the house water pressure, it was 110 psi!!!
So the plumber installed a PRV (Pressure Reducing Valve) and set it at 55-60 psi.
All is good now. No more leak.

As it turned out, the Grohe faucets (single-handle type) use a cartridge system that in my case starts leaking at around 110-120 psi.

Hope this helps others!