We have recently moved our old website to a new platform using Angular 2 + Universal. The site is city-sightseeing.com and while it was fine at the beginning in the last weeks we are having issues with SEO and being de-indexed.
Timeline of events, issues and solutions 29th March: New site launched only in English. All looking good and working fine. Redirects were made from the old site website to the new one using 301s for the pages we have in the new site. The content has all be re-written for the new site. 12th May: New languages added: italian, french, spanish and german. We put the hreflang in all the pages to tell Google about all languages. Issues started here. We saw that Google started giving us soft-404s and de-listing the english site from the listings. The new languages didn't seem to be affected. 24th May: after investigating we found a few issues that were fixed on this date. We changed how the default language was set to follow Google guidelines. We found that while we served the html code to Google the Fetch and Render in Search Console couldn't see our pages properly. We fixed that and now all our pages can be fully seen and rendered properly in Search Console. We reviewed our structured data to make sure it was working well. A new sitemap was uploaded with all the urls in all languages. We started seeing improvements and our pages, especially english ones which are the main ones for us, started appearing again in the searches and google index. Since then we didn't touch anything giving time to Google to go over the whole site.
Since few days ago we started seeing again the same issues as before. The pages are being de-indexed by google. The soft-404s started growing, these are only for the english pages. The structured data number of items started to go down. We double checked and the pages can be properly seen by the bot in the Fetch and Render tool.
Any ideas of what can be happening? Thanks!