Author: anders holck
1. After several attempts I have failed to provoke the general error.
This is probably a rare bug, but as you haven't given the exact steps to replicate, it's hard to debug and report. To get us further an exact and repeatable 'how to trig it' is needed.
2. By closing the canvas window, you automatically close all open sequences.
Therefore you cannot reopen the canvas or timeline window, without first opening a sequence. This is not a bug.