How can I avoid getting error code 0 on Google Custom Template request?

I use NativeCustomTemplateAd in my Android app to display some banners in my app's Home page screen. Lately I got some reports that on some occasions these banners are not displayed, so I've triggered an analytics event every time this happens. Turns out that it happens for more than 10% of my daily active users.

After a lot of research and a long discussion with someone from Google support, I've found out that:

• it happens on any Android version but more than 80% on Android 8.0.0
• if I restart the device that has this issue it will work again for a random period of time
• it's not a problem with my code (I've tried CustomRenderingExample from Google samples project)
• it's not from our DFP setup (again, I've tried with the sample DFP AD Unit ID)

• I've done some Charles debugging and I see that the following request https://googleads.g.doubleclick.net/mads/static/mad/sdk/native/production/native_ads.html returns an HTML 200 response which contains, among others, the following message:

  "Incorrect native ad response. Click actions were not properly specified",ha="Missing required native ads fields."

With me having tried pretty much everything to solve this issue, unsuccessfully, and with Google's support close to zero, this is my last take: has anyone encountered something similar when using NativeCustomTemplateAds? Is there anything that I can do to have it working on all of my daily active users?

Thank you!

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