Try going back to a 5.4.x.x. version of Blue Iris.

I have a very similar slow FPS issue on any 5.5.x.x. version.
on 5.4 I get 40-50 FPS.
If I upgrade to 5.5 I get <5 FPS
if I return to 5.4 I get 40-50 FPS

Maybe related?

System working great on 5.4.x.x

Upgrading to Any 5.5.x.x version causes the playback to slow to a crawl. 2-5 FPS
multi-camera or single camera, same issue.

No other changes.
I cna regress back to 5.4.x.x and all is fine again.

Thoughts?

Latest release has now solved this issue.
thanks!

In the latest update, the Split View on the iPad is broken.

When starting the app for the first time, with Split View enabled, the cameras will Not Show.

The Homescreen is 'stuck' taking 100% of the screen.