No result when trying to lookup timezone of Curacao

[th-otto]

When using the demo program, and the out_v1/timezone21.bin database, i get no result:

$ ./demo demo database/out_v1/timezone16.bin 12.1080 -68.9350
The simple string is [(null)]

When using any other database, i get the expected result:

./demo database/out/timezone16.bin 12.1080 -68.9350
In zone:
  meta: 2085
  polygon: 1039
  TimezoneIdPrefix: America/
  TimezoneId: Curacao
  CountryAlpha2: CW
  CountryName: Curaçao
Safezone: 0.204524
The simple string is [America/Curacao]

I also get expected result, when using one of the *21 databases.

(databases were downloaded from https://cdn.bertold.org/zonedetect/db/db.zip and not build locally)

PS: what does that "safezone" value tell? I can't find any documentation about it.