diff --git a/src/app/core/data/root-data.service.ts b/src/app/core/data/root-data.service.ts
index ef542199dd..035e14168f 100644
--- a/src/app/core/data/root-data.service.ts
+++ b/src/app/core/data/root-data.service.ts
@@ -12,7 +12,7 @@ import { HALEndpointService } from '../shared/hal-endpoint.service';
 import { NotificationsService } from '../../shared/notifications/notifications.service';
 import { HttpClient } from '@angular/common/http';
 import { DefaultChangeAnalyzer } from './default-change-analyzer.service';
-import { Observable } from 'rxjs';
+import { Observable, of as observableOf } from 'rxjs';
 import { RemoteData } from './remote-data';
 import { FollowLinkConfig } from '../../shared/utils/follow-link-config.model';
 import { FindListOptions } from './request.models';
@@ -20,7 +20,6 @@ import { PaginatedList } from './paginated-list.model';
 import { DspaceRestService } from '../dspace-rest/dspace-rest.service';
 import { RawRestResponse } from '../dspace-rest/raw-rest-response.model';
 import { catchError, map } from 'rxjs/operators';
-import { of } from 'rxjs/internal/observable/of';
 
 /* tslint:disable:max-classes-per-file */
 
@@ -75,7 +74,7 @@ export class RootDataService {
     return this.restService.get(this.halService.getRootHref()).pipe(
       catchError((err ) => {
         console.error(err);
-        return of(false);
+        return observableOf(false);
       }),
       map((res: RawRestResponse) => res.statusCode === 200)
     );
diff --git a/src/app/item-page/edit-item-page/item-delete/item-delete.component.ts b/src/app/item-page/edit-item-page/item-delete/item-delete.component.ts
index 7735fae0ea..4ea2622962 100644
--- a/src/app/item-page/edit-item-page/item-delete/item-delete.component.ts
+++ b/src/app/item-page/edit-item-page/item-delete/item-delete.component.ts
@@ -8,7 +8,9 @@ import {
   combineLatest as observableCombineLatest,
   combineLatest,
   Observable,
-  of as observableOf, Subscription
+  of as observableOf,
+  Subscription,
+  BehaviorSubject,
 } from 'rxjs';
 import { RelationshipType } from '../../../core/shared/item-relationships/relationship-type.model';
 import { VirtualMetadata } from '../virtual-metadata/virtual-metadata.component';
@@ -34,7 +36,6 @@ import { followLink } from '../../../shared/utils/follow-link-config.model';
 import { getItemEditRoute } from '../../item-page-routing-paths';
 import { RemoteData } from '../../../core/data/remote-data';
 import { NoContent } from '../../../core/shared/NoContent.model';
-import { BehaviorSubject } from 'rxjs/internal/BehaviorSubject';
 
 @Component({
   selector: 'ds-item-delete',
diff --git a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/dynamic-lookup-relation-modal.component.ts b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/dynamic-lookup-relation-modal.component.ts
index 69c2ac3b7f..74e2f4511e 100644
--- a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/dynamic-lookup-relation-modal.component.ts
+++ b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/dynamic-lookup-relation-modal.component.ts
@@ -1,5 +1,5 @@
 import { Component, EventEmitter, NgZone, OnDestroy, OnInit, Output } from '@angular/core';
-import { combineLatest as observableCombineLatest, Observable, Subscription } from 'rxjs';
+import { combineLatest as observableCombineLatest, Observable, Subscription, BehaviorSubject } from 'rxjs';
 import { NgbActiveModal } from '@ng-bootstrap/ng-bootstrap';
 import { hasValue, isNotEmpty } from '../../../../empty.util';
 import { map, skip, switchMap, take } from 'rxjs/operators';
@@ -29,7 +29,6 @@ import { RemoteDataBuildService } from '../../../../../core/cache/builders/remot
 import { getAllSucceededRemoteDataPayload } from '../../../../../core/shared/operators';
 import { followLink } from '../../../../utils/follow-link-config.model';
 import { RelationshipType } from '../../../../../core/shared/item-relationships/relationship-type.model';
-import { BehaviorSubject } from 'rxjs/internal/BehaviorSubject';
 
 @Component({
   selector: 'ds-dynamic-lookup-relation-modal',
diff --git a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/search-tab/dynamic-lookup-relation-search-tab.component.ts b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/search-tab/dynamic-lookup-relation-search-tab.component.ts
index f70f073743..fd1092d748 100644
--- a/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/search-tab/dynamic-lookup-relation-search-tab.component.ts
+++ b/src/app/shared/form/builder/ds-dynamic-form-ui/relation-lookup-modal/search-tab/dynamic-lookup-relation-search-tab.component.ts
@@ -4,7 +4,7 @@ import { SearchConfigurationService } from '../../../../../../core/shared/search
 import { Item } from '../../../../../../core/shared/item.model';
 import { SearchResult } from '../../../../../search/models/search-result.model';
 import { PaginatedList } from '../../../../../../core/data/paginated-list.model';
-import { Observable } from 'rxjs';
+import { Observable, BehaviorSubject } from 'rxjs';
 import { RelationshipOptions } from '../../../models/relationship-options.model';
 import { PaginationComponentOptions } from '../../../../../pagination/pagination-component-options.model';
 import { ListableObject } from '../../../../../object-collection/shared/listable-object.model';
@@ -23,7 +23,6 @@ import { RelationshipType } from '../../../../../../core/shared/item-relationshi
 import { Relationship } from '../../../../../../core/shared/item-relationships/relationship.model';
 import { SearchObjects } from '../../../../../search/models/search-objects.model';
 import { DSpaceObject } from '../../../../../../core/shared/dspace-object.model';
-import { BehaviorSubject } from 'rxjs/internal/BehaviorSubject';
 
 
 @Component({