Dual router: slave/master (non-synergy mode) power up issues

Client operates a fleet of buses with Br1 pro 5g where slave has LAN to primary WAN with different operator sims etc. this config has been working ok for some months on 8.2.1 but seemingly since 8.3.0 slave routers have been more inclined to hang after morning startup: hang shows solid LAN lights and unit is offline from IC2. Has anyone else encountered this issue?