Clients in separate subnets unable to communicate

Hello,

I have 2 machines advertising the following routes:

  • Machine A: 192.168.1.0/24
  • Machine B: 10.10.0.0/20

All clients behind each subnet are able to communicate via the subnet routers just fine, until today when Client A (192.168.1.10, Linux 3.2.0 ARMv7) and Client B (10.10.0.3, Debian 10) stopped communicating with each other. As far as I’m aware there are no firewalls present on each client (no firewalld, ufw is inactive).