Context can take minutes to change

[james-s-w-clark]

from #417

Possible issue:
In the Contexts screen, I am pressing Enter on a blue context with the => to show it's selected. But, my context isn't changing from the current yellow one.
Edit: It did, about 3 minutes later 🤔

This is with hundreds of contexts. Maybe it's much faster when there's only a few of them?