Spirit Theme Font Styling Anomalies

I am encountering problems with font styling – I think only on mobile devices and possibly only Chrome/Google.

As far as I can tell the font appears as it should – black on a grey background – on various desktop browsers, including Chrome.

When editing – in responsive mode – it is also appearing correctly.

It is appearing correctly on my iPad Pro when using Safari, though not Chrome/Google.

On my Android phone it does not render correctly in Chrome/Google but it does in Mozilla and Opera.

Any thoughts/suggestions?