The compress binary provided in package ncompress-4.2.4.4 with Tumbleweed and a
number of recent stable distributions produces garbled compressed data that
cannot be decompressed.

I can compile a binary that gives (exactly) the same garbled data by compiling
it with the wrong byte order. Note the flag -DBYTEORDER=1234:

cc -o compress  -DDIRENT=1 -DSYSDIR=1 -DUTIME_H=1 -DUSERMEM=800000
-DREGISTERS=20 -DIBUFSIZ=1024 -DOBUFSIZ=1024 -DBYTEORDER=1234
"-DCOMPILE_DATE=\"`date`\"" compress42.c

(produces garbled compressed data)

Reversing the byte order,

cc -o compress  -DDIRENT=1 -DSYSDIR=1 -DUTIME_H=1 -DUSERMEM=800000
-DREGISTERS=20 -DIBUFSIZ=1024 -DOBUFSIZ=1024 -DBYTEORDER=4321
"-DCOMPILE_DATE=\"`date`\"" compress42.c

(produces correct compressed data)

or using the provided build shell script gives a correct binary, that produces
correct data.