I love this plugin and have had it running on my multisite (on IIS) for the past year or so. I use it all at defaults as per your suggestion from a past question. It’s great.
I also use Defender Security by WPMU Dev to insert Security Headers e.g. X-Frame-Options, X-XSS-Protection and X-Content-Type-Options. I originally set that plugin up before I added Super Page Cache.
Today I decided to test and confirm the headers are still working, but they are gone.
If I disable Super Page Cache then the headers work again.
I’ve been looking through support tickets and plugin settings and I can’t figure out if I can fix it.
Is it maybe the setting named “Save response headers”? I won’t touch it unless you tell me to.
Thanks for any advice.