Ngxs not completly waiting for action to resolve successfully when using an action handler - ngxs

Question

after dispatching an action to post images to a backend API, a second action should be triggered. I try to accomplish this by using an action handler that's listening for that postAction to resolve successfully and then should execute the second action. But for some reason the second action get's executed before the first action really resolves successfully.
Does anyone know why?
postaction:
#Action(PostAttachment)
postAttachment(ctx: StateContext<EditEntityStateModel>) {
ctx.patchState({ currentlyUploading: true });
const previews = [...ctx.getState().previews.data];
return previews.forEach((preview, index) => {
//while (ctx.getState().jobsInQueue <= 100) {
previews[index].status = 'uploading';
ctx.patchState({
jobsInQueue: ctx.getState().jobsInQueue + 1,
previews: { ...ctx.getState().previews, data: previews }
});
return this.entityDataService
.postAttachment(preview, ctx.getState().selectedEntityId)
.subscribe(
progress => {
console.log(progress);
},
error => {
const updated = [...ctx.getState().previews.data];
console.error(error);
updated[index].status = 'error';
ctx.setState({
...ctx.getState(),
jobsInQueue: ctx.getState().jobsInQueue - 1,
previews: { ...ctx.getState().previews, data: updated }
});
},
() => {
const updatedAttachment = [...ctx.getState().previews.data][index];
updatedAttachment.status = 'success';
const updatedPreviews = [...ctx.getState().previews.data];
updatedPreviews[index] = updatedAttachment;
ctx.patchState({ previews: { ...ctx.getState().previews, data: updatedPreviews}});
ctx.patchState({
jobsInQueue: ctx.getState().jobsInQueue - 1,
previews: {
...ctx.getState().previews,
data: updatedPreviews.filter((_, position) => position !== index),
showEmptyMessage: !(updatedPreviews.length > 0),
},
currentlyUploading: updatedPreviews.length > 0
})
}
);
//}
});
action handler:
this.actions$.pipe(ofActionSuccessful(PostAttachment)).subscribe(() => {
const selectedEntityId = this.store.selectSnapshot(EditEntityState.selectedEntityId);
this.store.dispatch(new LoadAttachments(selectedEntityId));
})