Tile Failures and Problems

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Why is this happening?!? I have my guesses as I am familiar with concrete and what can be expected to some degree, but this is my first time screeding a mortar mix on a vertical surface, other than a small mock-up I did first. Substrate: Steel lath (expanded metal) over 15 lb felt over 1/2 in. plywood over 16 on center studs. Very old framing, not plumb flat or square in this 3 x 5 stall. Mix: 5, 1, 1, with 2 parts cold clean water. Parts thoroughly mixed dry with auger bucket mixer before adding water. Allowed to slack a bit before remixing Application to back (or long wall, with niche) began with two buckets of mud on the floor and swiping up the wall with 5 x 13 trowel to complete the first pass. By the time the screed strips were in the upper half of the float was starting to glaze over. Thinking that the second pass of mud would not bond well with the first, I scratched the surface of the first pass to "open it up". I proceeded with building up the mud layer and followed with the screed. Overall I felt like I was behind through the process as the mud was getting stiffer than I would have liked. In other words, too much time was going by and the mortar was getting stiff and less workable. On another day I tackled one end wall and the process went smoother with a minimally wetter mix, but to my surprise, and within just an hour or two from the screed, the cracking began. Even while the mud was soft enough to take a finger print I could push on the first crack that appeared and see the gap close. So I put a straight edge across the gap to confirm ridging along the crack. So much for the flat float I was hoping to achieve. I won't float the third wall until I know I don't have to tear out what I've done so far. But I am prepared to do that in favor of some wall board after some modification to the framing to achieve flat plumb and square. So, what went wrong? I have my guesses, but I'd sure like some input from someone who has a lot more experience than I. Thank you in advance. James Salem, Oregon