Hi @edd,
I was getting constant down alerts from my monitoring providers Pingdom and Freshping, that my system was going down about every 30 minutes.
The reports from them were something to do with the SSL, they were simply saying SSL Error.
I checked the expiry of the SSL and it says 4th Mar to 2 Jun 19. So they are current.
@Kfawcett suggested it may be CloudFlare. There are some plugins that use CloudFlare.
I removed the SSL from the monitoring alerts as I was getting over 60 a day and it was like cry wolf, I didn’t know if my system was actually down. I will get this investigated at my end, as well as report a bug.