wp invoice online invoice page broken styling

Hello I am having a recurring problem with viewing invoices online. The page styling appears broken and I am not sure why, it has happened before, I replaced the template files, cleared the cache and it fixed the problem, but it keeps doing this every couple of weeks.

I have tried switching off compatibility mode and then switching it back on, this sometimes fixes the issue? (I use the PDF addon which is fine, it is only when viewing online)

I love this plugin, but I would like to find a permanent fix this, does anyone have any ideas?

Thanks ??