Slowness in migrating content to site using Metalogix Content Matrix

Hi,

We would like to ask what are the common causes why there is inconsistency on the speed of migration. For a 5 mb site, sometimes it took 30 mins, sometimes it took 1hr, and there are also times it takes about 6 hrs for a small site content. Can you please help share thoughts about this. 

Also is there a way, a configuration or something to be done on Metalogix to speed up migration process. Please advise. THanks so much for the help.

Regards,

-Bryan