Coolant leaking?

My GTI has an apparent slow coolant leak. Today will be the third time I bring it in to the delaer to address. The first time (1.5 yrs ago) they just topped it off. The second time (1 year ago) they found a slow leak and ended up replacing the thermostat and I believe the water pump underneath that coolant was leaking on. Yesterday the warning light came on again and I noticed the reservoir was almost empty.

So either it is using coolant, they didn't fix the leak properly a year ago, or there is another leak. Either way, its more then annoying. My Jetta I had prior to the GTI never leaked or used coolant. The G12 bottle I bought just in case still sits in my storage room unopened.

Has anyone else had this issue?

Have them pressure test the system AND the overflow cap itself. Do you see any traces of coolant residue below the overflow bottle? If minor enough, it'll just be vapors, but it adds up. A "dirtier than the rest of the engine bay" passenger side frame rail is a good indicator of a vapor leak at the cap/bottle.

I couldn't find any signs of a leak on the passenger side, dirty, etc.

VW pressure tested it when I got there and said it had no leaks. They topped off the coolant and pressure tested again, and found no leaks. They said it was good to go.

It's perplexing...could it really be using coolant like that?
I'll get some G3 to have handy just in case.