Could you have uncovered a spring with the patio construction?

Let's see it. But no close-ups please.

I'll get some pics tomorrow. It will be tough to see as the mud just blends into the mulch and surrounding soil and the water eventually runs down a slope.

Attached are some pics. No rain in 72 hours and no irrigation. It really just shows as a very wet area. You cannot see where it is originating from. I hope the pics are far enough back (there is one close-up).

I believe you are correct NHBabs, it is water weeping from the wall. There is no sediment washing out yet but I am very concerned about the integrity of the wall.

So far it is just the sprinkler guys involved. If they find nothing then the patio installer will be called.

No idea the water source based on photos.

A paver patio is built on granular material that drains quite well. so there is no need for a drain under it. Even if the material under it becomes saturated, the patio surface will still shed water, and eventually the saturated material will still drain.

The rocks around the edge I would not call a retaining "wall." They act more as a curb. But since the curb is comprised only of individual rocks separated by soil, it, in itself, is not capable of preventing water from draining away. Nor should it be. The existence of the patio & curb seems separate from the problem of an unknown source of water infiltrating an area. (Other than that they could complicate the diagnosis and repair.) But it is enough water to look like a leak ... unless you happen to have a very high water table. If you do and there has been a lot of rain in days prior, that could cause such a condition.

Yardvaark, you may be on to something about the high water table. My sump pump runs quite frequently, the previous owner had to have the basement waterproofed, we have installed two french drains on both sides of the property and when it rains the runoff at the back property line in the swale is significant (to the point of thinking about a dry creek bed but most likely plant materials instead). If no leak can be found and there is no direct cause, should I be worried about the "curb" failing and the patio eventually falling apart? It is about 36 inches above grade at the end of the patio.

I don't know how you're measuring it, but the height of the rock curb does not look to be anywhere near 36". Looks more like 12". There is not much about it to fail. The soil would not wash out of it because the ground is wet. It would take moving water like hard rain and runoff. Presumably, you will plant something to grow in the cracks to lock the soil in place so even runoff cannot disturb it.

As a test for high water table, dig a couple of 12" or 18" deep holes (not too close to patio/curb) and see if they accumulate water over a day.

I did indeed mismeasure the curb. It is 20 inches off grade. I did that by standing on the flat stone with my yardstick hitting the ground.

Please reassure me that at this height, I am worrying for nothing! Water still trickling slowly but steady. Even if the wall/curb poses no risk, I am having a hard time getting the area ready for seeding as it is so wet.

I'm not saying there is no problem. I'm saying that it's not a problem likely to cause direct harm to the patio. But there is either a leak, or a high groundwater condition. If it is the former, you have to do whatever you can to find it (such as explore the irrigation system.) If it is the latter, it would likely be associated with recent rains and, if so, will diminish with the changing season. Then, I can't speculate on the long term possibilities.

If not the irrigation system as I mentioned previously it could be a spring. I don't know what area you live in, but springs are not uncommon here. With trickling water and sump pump kicking on frequently a spring is a possibility. If it is a spring you have a perfect opportunity for a small natural pond in that area. We were lucky that our first house had a spring in the back yard. We dug a smaller pond at the beginning of the trickle of water and put an overflow pipe at the other end. It was about 2 - 3 ft deep. Once it filled up and the dirt settled we added fish and seaweed from a local lake and landscaped around it. It rairly froze over in winter because of the constant movement of water in and out of the pond and formed its own eco system and we only had to feed the fish if we wanted to.