I have confirmed this behaviour. :-(
Almost certainly it is due to the use of "Passing a term through a $_GET or $_POST array" which is reserved term.
See https://codex.wordpress.org/Reserved_Terms
I propose we should amend the following in group/event lists functions that are (or might be) passed as $_GET attributes:
type -> list_type
day -> weekday
cat -> group_cat or event_cat
status -> group_status
I have confirmed this behaviour. :-( Almost certainly it is due to the use of "Passing a term through a $_GET or $_POST array" which is reserved term. See https://codex.wordpress.org/Reserved_Terms
I propose we should amend the following in group/event lists functions that are (or might be) passed as $_GET attributes: type -> list_type day -> weekday cat -> group_cat or event_cat status -> group_status