I have 94 hosts on one subnet, and discovery only ever manages to pull up the same 10 or so each time. If I manually add one of the hosts discovery missed, it all probes up fine with no problems.
Any suggestions on how to improve discovery?
You might try to change scan type from fast (by ping) to reliable (by services), maybe not all of your hosts respond to ping in some time that dude expects and therefore it treats them as non-existent.
cya
LePiaf