I don't know if anybody can help with this, but I trigger my events using a tombola system, one per region, for example:

rte_travel_event_tombola_d_albany = {
trigger = {
NOT = {
has_character_flag = rte_recent_event
}
location = {
geographical_region = d_albany
}
}
random_events = {
chance_of_no_event = {
value = 60
}
100 = rte_d_albany.1 # Dance of the Albany Maidens
100 = rte_d_albany.2 # The Albany Run
100 = rte_d_albany.5 # Lost in the Haunted Gardens
}
}

And then in the events themselves I have this in the trigger:

NOT = {
has_character_flag = rte_recent_event
}
location = {
geographical_region = d_albany
travel_danger_type = {
travel_plan = root.current_travel_plan
terrain = hills
}
}

And in my events I apply the rte_recent_event modifier:

immediate = {
(...)
add_character_modifier = {
modifier = rte_recent_event
days = 10
}
}

The modifier is properly applied, but it seems to have no effect to prevent events from triggering. Anybody would have an idea as to why? In fact I can have two or three events triggering on the same day occasionally... Help welcomed!