For everyone still searching...Had the same issue, allow access to custom networks enabled but still no ping. The solution for me was:
Remove offending routing rule in console:
ip route del 192.168.1.98 dev br0
Add new route rule to the shim network (custom network that is bridged with local unraid adapter:
ip route add 192.168.1.98 dev shim-br0
The result needs to be: