Playback painfully jerky, slow and stuttering.

[Corvus85]

Now it doesn't let me see Blue Iris on the 4k monitor and RDP at the same time - are you able to do so?

Yes, I'm able to see both at exactly the same time. That may be where the problem lies.
This also happens with Parsec.

 

[sebastiantombs]

Here's a very handy way to roll back to any version you might want to roll back to -

Blue Iris Update Vault

Blue Iris Updates (64 bit) - History

ipcamtalk.com

Blue Iris Software Updates

ipcamtalk.com

 

[LHuisingh]

I sometimes have stuttering. My usual goto is to restart my network. That usually gets things working better.