I found the source of the issue: firmware 2.1.7 has a bug that when sending remote command when ‘special station auto-refresh’ is turned off, it uses the maximum value 65535, but the manual control command (/cm) only accepts 64800 as the maximum value. Because of this discrepancy, the 65535 value is dropped, causing it to not respond to remote command. Turning on auto-refresh forces it to use a smaller run-time value (and relies on periodic refreshing to renew the command). We will fix this in the firmware as soon as possible.