I'm going to make a couple of unpopular statements here, so let me first start that no matter what, this is unacceptable and should be done over.... WITH A DIFFERENT TILE, or using a leveling system. First, you're shining a light right down the face of the tile, and even an acceptable tile job will look horrendous doing that. It's what's called "washed lighting" and there are very specific recommendations out from the TCNA concerning permanent installation of washed lighting with tile installations. Second-- I don't care WHOSE tile you use. narrow elongated tiles like these will be bowed, and if installed without a leveling system, will give the "basket weave" appearance that you see in the pics above. Sometimes, especially with porcelain tiles, you can take that bow out. Other times, especially with wall tiles that won't flex much, you can't, and then the only way to install them is with a 25% broken joint or even better, soldier coursing (normal grid pattern). One way or the other, the bottom line is the installer AND the person who sold you this tile, should have informed you before the tile was installed that this would happen, and recommend either less of an offset, or going with a different tile.

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 :):)???

I've read on this site that some (all?) extremely large format rectangular tiles tend to have some bowing to them due to the size and what happens during manufacturing. I believe Avanti (the pro above) is suggesting that you simply cannot avoid the lippage / visible bowing when doing a 1/2 stagger like your picture.

Here's the unintentional basketweave/3D effect you'll want to try to avoid (depends on how flat your tile is and the tile manufacturer recommended offset and downlighting in the shower certainly highlights the issue when it occurs): https://www.houzz.com/discussions/shower-wall-tile-lippage-done-an-redone-and-still-problems-advice-dsvw-vd~5218878 https://www.houzz.com/discussions/shower-tile-lippage-dsvw-vd~4695395