I just checked the Firewall Logs and see that
a huge Number of Blocks all related to Yandex appeared in the last 24 Hours
I checked the Bot Myself following Yandex recommended steps as described here
and all firewall blocks by Cloudflare in the last 24 Hours were wrong as this
accesses belonged to the legit Yandex Bot.
See here DNS Reverse Lookup
Despite that the Yandex Bot access the Webpage from a Legit IP Adress
the User Agent is also listed as Legit on their Website itself !
Mozilla/5.0 (compatible; YandexBot/3.0; +http://yandex.com/bots)
The main indexing robot. Yes
Mozilla/5.0 (compatible; YandexImages/3.0; +http://yandex.com/bots)
Indexes images to display them in Yandex.Images. Yes
So this is clearly something bad on the Cloudflare side as it blocks legit yandex bot.
Would be good if this can be fixed by Cloudflare.