I may add what installation I have.
BitwardenRS is installed in Docker on a Synology NAS, in a bridge network.
I have the DSM reverse proxy enabled for my domaine name.
I set this in addition to the reverse proxy of the domaine name :
May it be some delay I have to increase ?
I also run a script to made websocket notiications working (see this thread : [SOLVED] Websocket setup on Synology - Third Party Help - Bitwarden_RS Forum )
Those are working fine.