I have seen something similar, maybe it is your case:
If I have a database open and I have an updating query in the editor or just referenced from an import module then when I execute the result is displayed for a moment then immediately replaced by the open db display.
e.g.
import module namespace state="apb.state"; (: this has an update function :)
2
My workaround is just to work with no open db.
/Andy
When the size of the submitted query gets too large, GUI functionality
stops working: Results stop being highlighted in the tree or displayed in
the "text" window (which instead always displays the entire document). I
can run the exact same XQuery file through basexclient or a REST query
and everything works perfectly, so this appears to be strictly a GUI
concern.