Unreliable font in Sales Invoice

I have an unreliable signature in the sales invoice. Using the “Print” button, everything renders correctly. Sending a sales invoice via email, the signature doesn’t always load the font and sometimes defaults to a different font. Using the “PDF” button, also results in random usage of the font or a default one. The default one isn’t the default in the sales invoice so can look a bit jarring. Is there anyway to reliably load a nice signature font ?

I’ve considered using a base64 image, but this results in loads of lines in the sales invoice which isn’t ideal. Or an image signature, but a font is usually an easier way.

How I’m rendering the signature:

how I update my invoice - the base64 image signature I put in footer and changes in Font is in the font family in Theme and works fine. Print Preview will download our desired font, but in PDF its Manager IO default which is the Arial I guess