First, before I make any comment, let me ask you-- how tight are the grout joints? Also, could you take a pic and either post it, or send it to me, and I'll post it? I will say this much-- 5 feet a day is incredibly slow, and this thing should be impeccable at that pace. 60 feet of brick joint subway backsplash should've been tiled in a day and grouted the next.

That tile is gorgeous. I think it has to do with an uneven floor. However, your contractor should have addresses those areas by leveling. When I put laminate upstairs, my contractor laid out my entire master and realized several areas where it did just that. He pulled it all out and placed mats underneath certain spots to create an even surface before relaying. I know you can't do that daily with tile. What does your installer say?

A real tru tile setter can float there tile FLAT. We used to do this with wet setting on bigger tiles, Now we have medium bed thinset mortars that can be used up to 3/4" of depth under the tile so we can float to some extent with that. Floors are not always level and thats OK we are more looking for FLAT and in plane. If you start with a FLAT substrate that meets tolerances for TCNA/ANSI I dont always use lippage tuning. It comes down to a job by job basis, The quality of the tile, and many times the material budget. The one and only excuse for lippage is the tile material itself. If its warped / bowed etc. If the substrate is not in tolerance before I tile I know I have to float. If im floating I make sure its within 3/4" depth for my thinsets or I will sometimes wet set in which case I will level as I go.. Usually I fix the substrate first or skip on the job if they dont want to do that $$. But you dont get a floor with a bunch of lippage and I dont get a bad rep. Actual well installed marble floors can be polished and some lippage can be mandated. Its not cheap. We had a recent post here by one of our skilled veterans in it he speaks to bending tile with lippage tuning to force stagger patterns..... I have on occasion taken jobs with bowed tile and forced them somewhat into submission with Lippage tuning like that and it can really help (but thats not a spec and adviseable to try for many) lippage tuning doesnt LEVEL a floor it helps keep the tile flat and in plane. Leveling happens underneath and before tiling or via wet setting/floating. I have set 24x24 tiles with no tuning system just fine so you dont neccesarily NEED it always. Off topic: Its a great post you have here, we are in a market these days that tells people do it yourself, watch youtube and HGTV ....... as such weve got a bunch of novice diy tilers turned craigslist PRO that cant get the job done right. Usually half the price of A pros price and Homeonwers are getting the brunt of it while the entire tile industry remains largely unregulated on local levels and gets a bad rap daily here on Houzz... "Help Total tile debacle" " Why does my shower floor look wet " etc etc. But we dont get the full story, People claim to hire tile pros when in fact they show us no proof or paperwork, no company names, where they sourced the install etc. and I think a lot of what we see here on Houzz is folks hiring cheap labor off craigslist and trying to manage their own renos' getting in way past their depth and then coming on houzz complaining and not sharing all the facts thus making the entire PROFESSIONAL tile industry seem shady.. Not all of em but im sure its a serious number and I see it here in my own backyard all the time. Is that how you ended up here asking this :):)???

Unless you can prove that the subfloor was not perfectly done (sounds like they got it as close to flat as possible) then we have to look at the TILE. Tiles this large are almost always warped. The LEVEL of warping is now the question. As Sophie points out, you need to find out HOW warped is "warped". The easiest way to do so is to put two tiles "face to face" (pretty side to pretty side) and then "back to back" (ugly side to ugly side) and take PICTURES (if you can get a ruler or a measuring tape in the pic that would be even BETTER). Post those pics. And now the crucial part: who chose the tile (s/he who picked them is responsible for them)? Who gave instructions as to installation pattern (1/3 off-set, 1/5 off-set, 1/2 off-set, etc)? Who was on site to receive the tiles and signed off on them? Who gave the 1/8" grout line as the required amount? The person (or persons) who made all those decisions will have to answer to them. For this reason, many of the "outstanding" tile setters will insist on choosing their own tiles (or Kitchen Designers will insist on using their own suppliers) so that this does NOT happen. And Joseph is correct. The "worst offenders" are worth dealing with if the entire floor has lippage issues like this. The fix is often worse than the disease. As Sophie is fond of saying, "Lipstick on a pig." This is either a "live with it" or it is a complete redo.