What to do when FontBook says there is a serious error with the font? Do you still install it? How to fix the issue? Thanks

You can let us know which font it is, and which error it is.

Znikomit or Znikomitno24 for example

Font Znikomit (and ZnikomitNo24) include two Kerning Tables:
- old style 'kern' table
- new OpenType 'kern' table
I made so, because some Programs still don't work with new OpenType table.
I test this Solution at Windows and Linux, and it work without problems.
In my own Opinion it's not
"Serious problem [...] may cause system problems or even crashes".

I made Znikomit version for Macintosh, without old style 'kern' table.
Message about problems should not appear,
but You have to check whether Kerning is working properly in Your Program.

Font Znikomit for Macintosh in Znikomit-053forMac.zip is available on my site:

http://www.glukfonts.pl/font.php?l=en&font=Znikomit

Great, thank you so much. I will look at it and tell you if it works :-)

Hello yes I downloaded the font for mac and there was no errors anymore. Thanks a lot!

I got the same problem with the Dear Teacher font. But my problem was that it read <corrupt font name> and then Font basic parsability

I have the same problem wth EVERY font I have downloaded from DA Font in the past two days:

1 Serious error was found. Do not use this font.

And it repeats this after I click INSTALL

Serious problems were found with these fonts and may cause system problems or even crashes if installed.

here are some of the fonts I had this problem with

Chinese takeaway
Chinese wok food
Japanese

I get not one but three "serious errors" when I try to install FespiPalmer. It's a real shame, because I've been looking for a free Palmer Method font for a very long time, and this one didn't exist the last time I looked, so I was very excited when I found it. Alas…

Over 50 errors