New version crashes my site

I just saw that there is a new version of Inkblot and tried to update it. There hadn’t been a new version in a long time. The new version crashed my site and I had to revert.

I was getting a fatal error in header.php with line 38 related to inkblot_theme_preview(). I am using a child theme, and had made customizations to header.php. I tried to take my customizations and integrate them with the new header code, and the error went away, but instead my site had none of my extensive custom styles (which really restructure the whole site).

I am using this theme on two different sites for the same client and really would like to update it, but I am nervous now because of what I just experienced.

What are the differences between the old and new headers? And is there a difference in how they call the custom styles?
https://shinglestylehomeplans.com/
Thanks.