I think on some furnaces the sail switch is easily removed, but of course not on all. I am not familiar with your coach specifically but I am attaching a YouTube video on one that is easily inspected for function/operation....probably many of them are in a similar physical position on the blower unit. One thing you could try is banging the side of the fan housing when the thermostat calls for heat and motor is running in those first 30 seconds to see if the banging frees up the sail switch enough for the full gas start sequence to complete. The other is bypassing the sail switch electrically at the correct time in the start sequence, but I won't suggest doing that unless you are electrically knowledgeable. (could cause you more trouble otherwise).