Calendar images not showing on mobile view

When pulling events to a calendar, the corresponding events image displays on the proper date on the calendar. This works on both desktop and horizontal mobile view. However, in vertical mobile view (very possibly the most common way things are viewed these days), the image no longer appears. 

It seems I'm not the first one to struggle with this issue as I found the following threads... 

However, I was unable to find a solution. Can anyone help?

Just in case anyone else stumbles across this same issue, the closest I've found to a solution so far is this:

@media screen and (max-width:640px) {
td.has-event {
    background: gold !important;
    opacity: 1 !important;
}

- Posted by Tuanphan in one of the aforementioned listings.