If this is a PWA they are prone to caching everything. You need to clear this cache on exit. Plenty of documentation and solutions on this revealed in a quick search of Stack Overflow or the web.
Add the following to the end of your service-worker.js file
self.addEventListener('activate', function(event) {
event.waitUntil(
caches.keys().then(function(cacheNames) {
return Promise.all(
cacheNames.filter(function(cacheName) {
// Return true if you want to remove this cache,
// but remember that caches are shared across
// the whole origin
}).map(function(cacheName) {
return caches.delete(cacheName);
})
);
})
);
});