Clicking on a checkbox toggles other checkbox at times

So I got 5 checkbox. All below one another. They have been made using svg and polyline. When I click on the label of each checkbox, it toggles the correct one, but when I click on the image of the checkbox, at times it toggles the incorrect box!

.cbx {
  margin: auto;
  margin-top: 2px;
  -webkit-user-select: none;
  user-select: none;
  cursor: pointer;
}
.cbx span {
  display: inline-block;
  vertical-align: middle;
  transform: translate3d(0, 0, 0);
}
.cbx span:first-child {
  position: relative;
  width: 18px;
  height: 18px;
  border-radius: 3px;
  transform: scale(1);
  vertical-align: middle;
  border: 1px solid #9098A9;
  transition: all 0.2s ease;
}
.cbx span:first-child svg {
  position: absolute;
  top: 3px;
  left: 2px;
  fill: none;
  stroke: #FFFFFF;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
  stroke-dasharray: 16px;
  stroke-dashoffset: 16px;
  transition: all 0.3s ease;
  transition-delay: 0.1s;
  transform: translate3d(0, 0, 0);
}
.cbx span:first-child:before {
  content: "";
  width: 100%;
  height: 100%;
  background: #506EEC;
  display: block;
  transform: scale(0);
  opacity: 1;
  border-radius: 50%;
}
.cbx span:last-child {
  padding-left: 8px;
}
.cbx:hover span:first-child {
  border-color: #506EEC;
}

.inp-cbx:checked + .cbx span:first-child {
  background: #506EEC;
  border-color: #506EEC;
  animation: wave 0.4s ease;
}
.inp-cbx:checked + .cbx span:first-child svg {
  stroke-dashoffset: 0;
}
.inp-cbx:checked + .cbx span:first-child:before {
  transform: scale(3.5);
  opacity: 0;
  transition: all 0.6s ease;
}

@keyframes wave {
  50% {
    transform: scale(0.9);
  }
}

The html

<div class="ax-cb-div">
  <input class="inp-cbx" id="1" type="checkbox" style="display: none;"/>
  <label for="1" class="cbx"><span>
    <svg width="12px" height="10px" viewbox="0 0 12 10">
      <polyline points="1.5 6 4.5 9 10.5 1"></polyline>
    </svg></span><span>Checkbox number 1</span>
  </label>
</div>

<div class="ax-cb-div">
  <input class="inp-cbx" id="2" type="checkbox" style="display: none;"/>
  <label for="2" class="cbx"><span>
    <svg width="12px" height="10px" viewbox="0 0 12 10">
      <polyline points="1.5 6 4.5 9 10.5 1"></polyline>
    </svg></span><span>Checkbox number 2</span>
  </label>
</div>

<div class="ax-cb-div">
  <input class="inp-cbx" id="3" type="checkbox" style="display: none;"/>
  <label for="3" class="cbx"><span>
    <svg width="12px" height="10px" viewbox="0 0 12 10">
      <polyline points="1.5 6 4.5 9 10.5 1"></polyline>
    </svg></span><span>Checkbox number 3</span>
  </label>
</div>

<div class="ax-cb-div">
  <input class="inp-cbx" id="4" type="checkbox" style="display: none;"/>
  <label for="4" class="cbx"><span>
    <svg width="12px" height="10px" viewbox="0 0 12 10">
      <polyline points="1.5 6 4.5 9 10.5 1"></polyline>
    </svg></span><span>Checkbox number 4</span>
  </label>
</div>

Select checkbox 1, 2, 3, 4. Then click on checkbox 3 to uncheck it. Checkbox 4 gets unchecked instead. Upon clicking again on checkbox 3, it gets unchecked.

Link to codepen