depends on bug 701098 and bug 701100
Created attachment 597452 [details, diff]
Can you reproduce #701078?
The version bump could be a solution.
However we usually do not add alpha releases unless there is a good reason.
What do you think about a bump to the latest stable release?
#701078 happens reproducibly for me.
Upstream seems to be "over" the 1.x series, and has put quite some effort into making the slotting seamless, so I think that bumping is probably the least friction.