What kind of bugs appear with bigger default page sizes?

Lots of userspace makes assumptions about page size being 4k and breaks when it changes. Try looking for:

https://www.google.co.uk/search?q="pagesize"+"64k"+"bug"

https://www.google.co.uk/search?q="pagesize"+"64k"+"issue"

Another common one is actually in the kernel where filesystem block sizes are limited to page sizes, so from this point of view large page sizes are better:

https://lwn.net/Articles/591690/