Primefaces Tree : The checkbox selection gets deselected when I click on the button to open modal on the parent / child node

Hi I'm using the component Tree - Selection with the variant Checkbox. Everything in the component is working fine but I need to put a button next to every parent and child of my nodes to open a model which happen with the id of that node, the problem is that if I press the button that unchecks that node. This is my code

 <p-tree [value]="casePartyServiceContactModel" selectionMode="checkbox"
                                    [(selection)]="selectedServiceContactsTree" (onNodeSelect)="nodeSelect($event)"
                                    (onNodeUnselect)="nodeUnselect($event)">
                              <template let-node pTemplate="default">
                                <span class="listname"></span>

                                <span class="listicons pull-right" *ngIf="!node.parent">
                                <button type="button" class="btncontact btn-primary box mar-r-20 pad-t-2 pad-b-2" data-toggle="modal" (click) = "setCasePartyIdForServiceContacts(node.data.partyID,node.data.caseId)"
                                        data-target="#addServiceContactToCase">Add Service Contact To Case
                                </button>

                                </span>

                                <span class="listicons pull-right" *ngIf="node.parent">
                                           <button type="button" class="buttonicon blueicon" data-toggle="modal"
                                                   data-target="#viewservicecontactdetails"
                                                   pTooltip="View Service Contact Details"
                                                   (click)="getServiceContactDetail(node.data.serviceContactID);"
                                                   tooltipPosition="top">
                                                     <i class="fa fa-user" aria-hidden="true"></i>
                                            </button>
                                            <button type="button" class="buttonicon blueicon" data-toggle="modal"
                                                    data-target="#viewattachedcaselist"
                                                    pTooltip="View Attached Case List"
                                                    (click)="attachedCaseList(node.data.serviceContactID,node.data.firstName,node.data.lastName)"
                                                    tooltipPosition="top">
                                              <i class="fa fa-paperclip" aria-hidden="true"></i>
                                            </button>

                                            <button type="button" class="buttonicon blueicon" pTooltip="Detach Contact"
                                                    *ngIf="node.data.editableFlag"
                                                    (click)="detachContact(node.data.serviceContactID,node.parent.data.caseId,node.parent.data.partyID,false)"
                                                    tooltipPosition="top">
                                              <i class="fa fa-trash" aria-hidden="true"></i>
                                            </button>
                                        </span>
                              </template>
                            </p-tree>