Unreliable font requests - css

Question

I have a CSS file that loads two fonts into my webpage. Half of the time it works just fine, and half of the time the font requests fail with failed to decode downloaded font.
CSS
#font-face {
font-family:'oswald';
src: local('Oswald Regular'),
url(../fnt/font-oswald/Zm9udA_b3N3YWxk.eot);
src: url(../fnt/font-oswald/Zm9udA_b3N3YWxk.eot?#iefix) format('embedded-opentype'),
url(../fnt/font-oswald/Zm9udA_b3N3YWxk.woff2) format('woff2'),
url(../fnt/font-oswald/Zm9udA_b3N3YWxk.woff) format('woff'),
url(../fnt/font-oswald/Zm9udA_b3N3YWxk.ttf) format('truetype'),
url(../fnt/font-oswald/Zm9udA_b3N3YWxk.svg#oswald) format('svg');
font-weight:400;
font-style:normal;
}
#font-face{
font-family:'icon-general';
src: url(../fnt/icon-general/aWNvbg_Z2VuZXJhbA.eot);
src: url(../fnt/icon-general/aWNvbg_Z2VuZXJhbA.eot?#iefix) format('embedded-opentype'),
url(../fnt/icon-general/aWNvbg_Z2VuZXJhbA.woff2) format('woff2'),
url(../fnt/icon-general/aWNvbg_Z2VuZXJhbA.woff) format('woff'),
url(../fnt/icon-general/aWNvbg_Z2VuZXJhbA.ttf) format('truetype'),
url(../fnt/icon-general/aWNvbg_Z2VuZXJhbA.svg#icon-general) format('svg');
font-weight:400;
font-style:normal;
}
Oswald use
h1,h2,h3,h4,h5,h6{font-family:oswald}
Icon-general use
[data-icon]:before {
font-family: 'icon-general';
content: attr(data-icon);
font-style: normal;
font-weight: 400;
font-variant: normal;
text-transform: none;
speak: none;
line-height: 1;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale
}
CSS linking in HTML file
<link rel="stylesheet" href="/css/static.css">
Note that: it might be useful to know that no Content-Type headers are set in the font requests, that may be why there is trouble decoding the files.