Ionic Infinite Scroll

Hi,
I have developed an app with dynamic list inside dynamic slider . My problem is the infinite scroll not firing everytime . i have no idea where am doing the mistake. Including my html code below
Am using ionic 4

#tag {{postType.Name}}
<ion-slides #SwipedTabsSlider (ionSlideDrag)="animateIndicator($event)"
            (ionSlideDidChange)="updateIndicatorPosition()"
            (pan)="updateIndicatorPosition()"
            [pager]="false">
    <ion-slide *ngFor='let postType of postTypes ; let i = index' id={{postType.Name}}>
        <!--<div>-->
            <ion-content>
                <ion-list *ngIf="PostArray[postType.Name].Post!=null">
                    <ion-item *ngFor="let post of PostArray[postType.Name].Post">
                        <div class="cmt_homelist">
                            <div (click)="fnViewDetails(post.EncCreatedBy)" class="cmt_homelist_hdr">
                                <span class="cmt_hmelistprfpic">
                                    <!--<img src="{{fileUploadUrl}}{{post.CreatedUserImage}}" />-->
                                    </span>
                                <h4>
                                    {{post.CreatedUserFirstName}} {{post.CreatedUserLastName}}
                                </h4>
                                <h5>
                                    {{post.CreatedUserPosition}}
                                </h5>
                                <span class="cm_hmpost_type">
                                    <label class="cm_hmdate">{{post.DateDifference}}</label>
                                    <label class="cm_hmtype">{{post.PostType}}</label>
                                </span>
                            </div>


                            <p class="cmt_hmedetailstx">{{post.Description | truncate : paragraphLength : " " }}<label class='cmt_more_btn' *ngIf="post.Description.length>paragraphLength"> see more... </label></p>
                            <!--<<button *ngIf="post.Description.length > paragraphLength">see more</button>--->
                            <span class="cmt_hmelistmanpic">
                                <img src="{{fileUploadUrl}}{{post.Thumbnail}}">


                            </span>
                            <span class="cmt_hm_lstcntnt_ttlt">
                                <label>title</label>
                                <a href="#">test</a>
                            </span>
                            <span class="cmt_homelist_ftr">
                                <label>2 Comments</label>
                                <a href="#">See full post</a>
                            </span>


                            <!--<span>{{post.Title}}</span>-->
                        </div>

                    </ion-item>
                </ion-list>
                <ion-infinite-scroll (ionInfinite)="doInfinite($event,postType.Name)">
                    <ion-infinite-scroll-content></ion-infinite-scroll-content>
                </ion-infinite-scroll>
            </ion-content>
        <!--</div>-->
    </ion-slide>
</ion-slides>