Just cross-linking to this other related thread:
2 Way Audio - Low Volume via Hik Connect app
@Dan has raised it with Hik Tech Support UK this morning.
Hikvision has "re-released" firmware V.5.7.12 dated 01 Dec 22 with an update (same revision) dated 31 Jan 2023.
The release notes are dated 07 March 2023. See here. https://assets.hikvision.com/prd/public/all/files/202303/Network Camera-V5.7.12 Release Note-G5.pdf
Link to firmware here. DS-2CD2387G2-LSU/SL