lucemw, prior to 2016 as Rob said we have air assisted hydraulic brakes. The emergency brake automatically sets when you place the trans in P. On my prior A the air brakes had to be set manually. Not sure what Jayco implementation is. Also on the class A (not sure if this is related) when you shut the engine off while in N vs P, you get unusual results. One more thing, if you start the engine and roll in N you will get dinging...it expects you to be in a gear if you're moving.
A call to Seneca support line may be appropriate if no one has had an experience like yours.
2015 Jayco Seneca 36 FK
2016 Jeep Wrangler Unlimited tow
2010 Tiffin RED 36 QSA - gone
2011 Monaco Monarch class A - gone