I have EXACTLY the same symptoms with dude 4.0 beta1, beta2, beta3 on RouterOS even on clean database.
Tried fresh install on RouterOS 4.x and 5.0 running in Virtual machine in RouterOS KVM.
I cannot export immediately after installation (empty database) and with 1 dummy object added. When I push export - export file is prepared and I get disconnected during file download.
System has 512M of ram (492M free) and 512M of disk space (446M free so it is not a ram/hdd space problem.
Debug log shows that right after disconnect dude seems to be re-initialized:
12:30:39 store,debug adding system drive: primary-master (/dev/hda)
12:30:39 store,debug dude1: disk setup finished successfully
12:30:39 store,debug web-proxy1: disk setup finished successfully
12:30:39 store,debug activating store for dude1
12:30:39 store,debug dude1: activation finished successfully
Looks like attempt to export data just crashes dude instance.
Export is OK if I install dude on master host, not in VM.
Any comments from MiktoTik?