XAVC-I 1080p50 growing files export slow

Hello, my problem is that the export of a Premiere sequence with growing files source material in XAVC-I 1080p50 via the Media Encoder is very slow (30min sequence in ~12min) as long as the growing file is not yet completed.
As soon as you stop the recording of the XAVC-I file and thus finalize the file, the export is much faster (30min sequence in ~3min)

The comparison workflow in DNxHD 1080p50 also works perfectly with unfinished growing files (30min sequence in ~3min).

Premiere Pro 2024 / Adobe Media Encoder 2024
Growing files are created with EVS IPDirector

Premiere sequence settings for both Exportcodecs:
DNX 1080p, 50 frames/sec
Preview: DNX SQ 1080p 50

There are no 50p sequence settings for XAVC-I

I'm looking for a “same as source” workflow with growing files for XAVC-I 1080p50 - preferably without reencoding, so that it works as quickly as possible.

Where can I look for my mistake?