Video Preview: Transition effects cause 'Media Pending' when the file format is 'I-Frame Only MPEG'

I'm running windows 11, on  premiere version 25.5.

System Model Z690 AERO G DDR4

Processor 13th Gen Intel(R) Core(TM) i5-13400F, 2500 Mhz, 10 Core(s), 16 Logical Processor(s)

Installed Physical Memory (RAM) 96.0 GB

GPU NVIDIA GeForce RTX 4070

Rendering a video preview in file format 'I-Frame Only MPEG' causes media pending errors where I use a transition in the timeline. I've got Maximum Bit Depth, Maximum Render Quality, Composite in Linear Colour checked. If my file format is anything else this doesn't happen. 

I can use the trick to enable and disable the footage to fix this everytime, but it's not a great sollution. 

Any advice would be useful, as I'd prefer to preview my footage in this file format. 

Thank you,