I originally made a post about this on Rrls' Github page here, but the developer suggested reporting this to Replay Mod too.

If you attempt to render a replay shot while having a resource pack active and Rrls installed, the reloading bar will breifly appear and disappear again before loading, then the replay shot will refuse to render. You'll be stuck on the "Frames Rendered: 0/X" screen until you manually crash your game.

• This is NOT the case when no resource packs are active.
• This is NOT the case when Rrls is not installed.

(Closing this issue as it's no longer relevant - the bug has since been fixed by the developer of Rrls)