If the engine always starts up in conventional mode, it is missing the DCS watchdog. Everyone is entitled to their opinion but mine is if it doesn't start up silently (in command mode) then no point trying to add it with the remote, fussing with the App, etc.. This is given that the engine operates perfectly in conventional and your other PS engines work fine in command.
As for something you can do "at home" all I can suggest is visually check the integrity of the unique component on the PS2 5V board which picks off the DCS command signal (and watchdog) from the track voltage. It should look like this. It's unbelievably improbable but maybe the ferrite donut is cracked, or one of the 4 connections is improperly soldered to the board, or whatever.
