Looking at common\on_actions\00_on_actions.txt it seems as that colonial events are more likely to trigger and exclude Dutch Republic events. After becoming a huge colonial power, you get 1 Dutch Republic event every 30 years in average. My suggestion is to either increase the likelihood of Dutch Republic events OR create a separate pulse. I actually don't understand why both colonial and DR events are in the same pulse.
Code:
# country random events
on_thri_yearly_pulse = {
random_events = {
# Colonial Nations
100 = colonial_nation.1
100 = colonial_nation.4
100 = colonial_nation.10
###
# Dutch Republic
200 = dutch_republic.1
200 = dutch_republic.2
200 = dutch_republic.3
###
300 = 0
}
}