For me, the error was caused by a rounding error.
this style rule exists
.btn {
line-height: 1.42857;
}
which should be
.btn {
line-height: 1.42857143;
}
Turns off boot import in other SASS files, resulting in loss of precision. For the SASS compilation process, the checkbox --precision 8worked correctly.
For you, however, as indicated in another answer, you just need to put the icon in a different tag.
<span class="input-group-btn">
<button type="button" class="btn btn-default color-red">
<span class="glyphicon glyphicon-remove"></span>
</button>
</span>