Here is how I did it in the end. Knowing that the load failed when importing revision 327 :
# Move the first 4 lines of the dump to new file
head -4 ~/xxx_modules.svn.dmp > partial.dump
# Find out where is the beginning of revision 327 that failed
grep -n "Revision-number: 327" ~/xxx_modules.svn.dmp
# Copy content of dump from that line (change X)
tail -n +X ~/xxx_modules.svn.dmp >> partial.dump
# Load using this partial dump
svnadmin load --parent-dir Software/xxx_modules /xxx/zzz/ < partial.dump