iphone 16p frameloss when shot 4k120 hevc with external disk

iphone 16 pro popups frameloss hint ( "!" on record button) when i shooting at 4k120 hevc with external disk.

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it works fine when shooting at 4k60 hevc.

i tested the external disk r/w performance on iphone 16 pro, it's about 800MB/s read and write.
please help thx.

I get this problem too, and cannot seem to get any help at all.