After upgrading to 2021 selecting H.264 in Premiere Pro or Media Encoder freezes the app

[defaulty3ujje3bdvmg]

New issue for me. I upgraded both Premiere Pro and Media Encoder to 2021 and now when I select H.264 to encode, it causes the interface to lock up - before clicking render and I have to use task manager to end the application. Every other format is selectable and I can start the render.

Any ideas?

[defaulty3ujje3bdvmg]

Update: Workaround that I have found is to open ME and import the sequence there. H.264 is selectable and renders without issue using this workflow.