Strange phenomenon during video playback

Dear community,

we run a large streaming farm here, and have had a very strange phenomenon reported by a customer:

When we play a HLS (VOD) stream from our CDN on Apple devices with Apple software (AppleTV, Quicktime or Safari on MacBook, within our IOS app, native player in safari), it happens every 10 seconds (probably at the chunk borders) that the second to last frame is played twice and the last one not at all.

It seems, that the phenomenon has nothing to do with the files - on Apple hardware without Apple software, e.g. Chrome on Macbook, or all other devices like Windows PCs the phenomenon does not occur.

Does anyone have an idea what the problem could be?

Thank you and best regards Thomas