i just used the same files located in xtool 0.4.2
and here are my pics
Screenshot_1.png
It compressed just fine with no errors
Screenshot_2.png
here are the files for xtool 0.4.2 as you can see it created a freearc1.tmp file
Screenshot_3.png
here are the files that i was test packing
my arc.ini is
[External compressor:xtool]
header = 0
packcmd = xtool.exe precomp -mzlib+preflate -c32mb -t85p - - <stdin> <stdout>
[External compressor:lolz]
header = 0
packcmd = lolz\lolz_x64.exe -d256 -dt -dtb1 -mtt1 -mt14 -fba1024 -tt5 -mc128 $$arcdatafile$$.tmp $$arcpackedfile$$.tmp
[External compressor:srep]
header = 0
packcmd = srep\srep.exe -m3f -l512 $$arcdatafile$$.tmp $$arcpackedfile$$.tmp
my pack.bat file is
arc.exe a -ep1 -r -ed -s; -w.\temp -mxtool+srep+lolz data.bin "pack\*"