Problems running simple app under Tomcat with context

I have a simple Vaadin Flow app (with SpringBoot integration) deployed under Tomcat as war file. App is running fine in dev mode localy, but when deployed in container under context, its not showing anything. When I look into page source I can see polymer resources URLs start with “/frontend/” so context is not honored and browse cant load it. Whats more I can see in page source that some URLs star with “./frontend/” and some with “/frontend/” see example below. I tried this and that but can’t figure out how to make Vaadin to generate URLs to be relative or to honor context given by Tomcat container. Any idea whats wrong here?

<link rel="import" href="/frontend/bower_components/polymer/lib/utils/array-splice.html">
<link rel="import" href="/frontend/bower_components/polymer/lib/mixins/gesture-event-listeners.html">
<link rel="import" href="/frontend/bower_components/polymer/lib/elements/dom-if.html">
<link rel="import" href="/frontend/bower_components/polymer/lib/mixins/properties-changed.html">
<link rel="import" href="/frontend/bower_components/polymer/lib/utils/gestures.html">
<link rel="import" href="/frontend/bower_components/polymer/lib/elements/array-selector.html">
<link rel="import" href="/frontend/bower_components/polymer/lib/legacy/polymer.dom.html">


<link rel="import" href="./frontend/bower_components/vaadin-button/theme/lumo/vaadin-button.html">
<link rel="import" href="./frontend/bower_components/vaadin-ordered-layout/theme/lumo/vaadin-vertical-layout.html">