These plots do not show the first tick label on the left:
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-.41, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-.42, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-.43, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-.44, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-.51, 1.05}, None}]
But these work fine:
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-1.41, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-1.42, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-1.43, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-1.44, 1.05}, None}]
Plot[Sin[x], {x, -4, 4},
Ticks -> {{#, "Z = " <> ToString@#} & /@ {-1.51, 1.05}, None}]
Am I missing something, or possibly a bug?