These are corrupted files. THey are corrupted because of a hardware malfunction. If you are not seeing a similar issue inside of Lightroom Classic, then the likely candidates are malfunctioning hard disk, and malfunctioning memory chips.
These are straight up imags that seam to become effective once exported. This does not happen to every image image in the batch, just a handfull will look like this. I have added examples below in the chat.
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