Infinite loop with v-for inside a v-for - vue.js

Question

Can someone help me find out how I can achieve a loop inside a loop to print out a report of people and peoples annual leave.
Basically I have this:
<div v-for="user_list in user_list_filtered()">
<div class="user_heading"><h2>{{ user_list.first_name }}</h2></div>
<div class="report_content" v-for="user_leave in user_leave_filtered(user_list['.key'])">
<div class="first_date_content">
{{ user_leave.start_time | formatDate }}
</div>
<div class="days_taken_content">
{{ checkLSL(user_leave.hours, user_leave.type, false) }}
</div>
</div>
<div class="leave_content">
<div class="total_leave_title">
Total Leave Taken
</div>
<div class="total_hours">
{{ getTotalLeave() }}
</div>
</div>
</div>
So this iterates through a Firebase DB and gets all of the users, it then loops through each user one by one and using the [.key] finds that users leave and loops through all of the leave as it outputs. Then onto the next user and there leave.
While this works it will continue to loop infinitely and says in my console.
vue.esm.js?efeb:591 [Vue warn]: You may have an infinite update loop in a component render function.
Can someone explain maybe a better way to do this without the infinite loop or a solution to avoid it constantly looping?
Thanks
EDIT
Filter functions
user_leave_filtered(userPassed) {
var self = this
return this.userLeave.filter(function(i) {
if (i.users_id === userPassed &&
((i.start_time >= self.getUnix(self.firstDate) && i.start_time <= self.getUnix(self.lastDate)) ||
(self.firstDate === null || self.firstDate === '' || self.lastDate === null || self.lastDate === ''))) {
return true
} else {
return false
}
})
},
user_list_filtered() {
var self = this
return this.userList.filter(function(i) {
var passed = false
if (self.userToShow === i['.key'] || self.userToShow === 'All') {
// Track whether to filter out this leave or not
self.userLeave.forEach(function(element) {
if (element.users_id === i['.key']) {
passed = true
}
})
}
return passed
})
},

Answer 1

The cause was a function (checkLSL()) I was using to calculate some totals through the loops. I have some info on how to fix and seems to be working fine.
Thanks