#74 pngcrush/libpng fails with " Wrote palette index exceeding num_palette"

I'm using pngcrush for our website. Recently we updated from 1.7.83 to 1.8.10 and now some of our pngs cannot be compressed anymore.

I use the macOS executable from this repository: https://github.com/imagemin/pngcrush-bin/tree/master/vendor/osx

Output with pngcrush 1.8.10

| pngcrush-1.8.10
 |    Copyright (C) 1998-2002, 2006-2016 Glenn Randers-Pehrson
 |    Portions Copyright (C) 2005 Greg Roelofs
 | This is a free, open-source program.  Permission is irrevocably
 | granted to everyone to use this version of pngcrush without
 | payment of any fee.
 | Executable name is pngcrush
 | It was built with   bundled libpng-1.6.26
 | and is running with bundled libpng-1.6.26
 |    Copyright (C) 1998-2004, 2006-2016 Glenn Randers-Pehrson,
 |    Copyright (C) 1996, 1997 Andreas Dilger,
 |    Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
 | and bundled zlib-1.2.8.1-motley, Copyright (C) 1995 (or later),
 |    Jean-loup Gailly and Mark Adler,
 | and using "clock()".
 | It was compiled with gcc version 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1).

  Recompressing IDAT chunks in input.png to test.png
   Total length of data found in critical chunks            =       754
While converting input.png to test.png:
  pngcrush caught libpng error:
   Wrote palette index exceeding num_palette

   Critical chunk length, method 150 (ws 14 fm 0 zl 4 zs 0) =       854
CPU time decode 0.000622, encode 0.000896, other 0.001590, total 0.003848 sec

Output with 1.7.83

 | pngcrush 1.7.83
 |    Copyright (C) 1998-2002, 2006-2015 Glenn Randers-Pehrson
 |    Portions copyright (C) 2005       Greg Roelofs
 | This is a free, open-source program.  Permission is irrevocably
 | granted to everyone to use this version of pngcrush without
 | payment of any fee.
 | Executable name is pngcrush_17
 | It was built with libpng version 1.6.16, and is
 | running with  libpng version 1.6.16 - December 22, 2014

 |    Copyright (C) 1998-2004, 2006-2015 Glenn Randers-Pehrson,
 |    Copyright (C) 1996, 1997 Andreas Dilger,
 |    Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
 | and zlib version 1.2.8, Copyright (C) 1995-2013,
 |    Jean-loup Gailly and Mark Adler.
 | It was compiled with gcc version 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.56).

   Recompressing IDAT chunks in input.png
   Total length of data found in critical chunks            =       754
   Critical chunk length, method   1 (ws 14 fm 0 zl 4 zs 0) =       866
   Critical chunk length, method   2 (ws 14 fm 1 zl 4 zs 0) >       866
   Critical chunk length, method   3 (ws 14 fm 5 zl 4 zs 1) >       866
   Critical chunk length, method   4 (ws 14 fm 0 zl 9 zs 1) =       842
   Critical chunk length, method   7 (ws 14 fm 0 zl 9 zs 0) =       815
   Best pngcrush method = 0 (settings undetermined)
     for output to test.png
     (no critical chunk change)
     (no filesize change)

   CPU time decoding 0.001, encoding 0.003, other 0.001, total 0.006 sec.

The file is attached.

[Anonymous]

Just noticed the same also happens with 1.7.83 if I use the -reduce flag