UBBthreads is old and a lot has been developed since then that may or may not affect the behavior of our forums.
Software comes and goes system becomes obsolete or depreciated.
Even though its not a direct forum script issue. Just addressing that our forums are affected and communicating around it helpes.
What Gizmo and Ruben did guided me bit by bit towards the solution. it steered me towards the logs and eventually I found my own logs and from that I did what Ruben suggested I disabled not exactly what he said asked for but the OWASP that I found in the logs.
So from my point of view I'm satisfied and possible if someone else looks for similar info he can always search for it here now when its been documented.
If you go to Cloudflare > Security > WAF > Managed rules - you can read about it.
Cheers