Proxy playback stops when playing fast forward

Hello,

Whenever I create proxies, either DNxHR or ProRes, the playback (of the proxy) will freeze, and the audio will keep going in the background.

This happens only when playing FAST FORWARD, not when playing at normal speed.

It doesn't happen right away, at first it's very smooth, much more than the original file (as it should be), but after a minute or less this issue starts to appear.

EDIT:
I tried creating H.264 proxies, which I thought would perform even worse, but they are smooth like butter. Who knows!

Thanks,

Daniele