Android purges firewall rules after network disable/airplane mode.
Setting my phone to disable data access and/or enable airplane mode seems to cause the transproxy iptables rules created by OrBot to get silently flushed. After re-enabling, all apps access everything without tor, until I go into the orbot config screen to cause it to reapply them.
OrBot should listen for these network disable/loss/disconnect events if possible, and reinstate the iptables rules after this happens.
Someone should also test if switching from cell data to+from wifi also triggers this iptables reset. I have not tested that yet.