Resolving a font conflict

So I just recently upgraded to 5.3.x.x.x.x.x and have noticed that there’s some form of font conflict with my Souvenir LT font I use for a lot of my documents (appears as boxes). I had thought something had affected the font and checked but it’s usable and visible in other programs. I didn’t realize LibreOffice included it’s own fonts as well. So I’m wondering how I can fix this font conflict (perhaps rebuilding the font cache, but I don’t know how), or if I need to regress to an earlier version of the program, and if so, what.

What operating system?
I can tell you how to clear the font cache on Windows and Linux.
Don’t know on Mac.

There are a lot of different Souvenir LT fonts out there.
Please post a link to the font file you are using so I can test.

I’m using Mac OS X 10.11.6. As to the font, it was one that came with CorelDraw 9 years ago. I wouldn’t know where to link to it.

Rolling back to the 5.2 version seems to have fixed the issue. Other comments have suggested it has connections to the new rendering.

LibreOffice 5.3 dropped support for Adobe Type 1 fonts.
Given that the font is that old and on a Mac my guess is it is a Type 1 font.
So using LibreOffice 5.2 is a workaround.

Going forward you may want to either find an OTF replacement, or convert it yourself.
It is easy to find Souvenir Light OTF and TTF fonts for download.