Thank you for reporting.
We will be needing more information in order to pinpoint the issue that you are having. Please read the pinned post and fill out the bug reporting form in it, as well as providing a pastebin link to an output log from when the issue occurred. The location of output logs and the instruction on how to use pastebin to upload it is also in the pinned post.
I have seen that bug when A20 first released, and had thought that it has already been fixed. Once we get the necessary information, maybe we could find out how to reproduce and fix it.