When an audio clip is loaded in the source monitor, its video resolution on an external monitor (via a blackmagic decklink 4k extreme) switches to 1080/25p, while my timeline is 1080/50i. can this be avoided?

When an audio clip is loaded in the source monitor, its video resolution on an external monitor (via a blackmagic decklink 4k extreme in my case) switches to 1080/25p, while my timeline is 1080/50i.
Could this be avoided? It creates constant switches on the external monitor while editing. I have look around but haven’t found a solution.
I thought I remembered that Blackmagic could lock the output to a fixed resolution, but it might be a false memory, as I haven’t found it anywhere!

Can something be done on Premiere side?