Continuing the hijack, just a little... Slab on grade with post-tension cables (PTCs) is essentially the standard in N.TX, and has been for 30-40yrs...
Most VFDs state the units of accel/decel rate as Hz/sec, and default on most units I've worked on is 1 (hz/sec), so 1 minute to start or stop. ...Out...
By panhandle standards I'm just around the corner (about 20 miles south of your McKinney corner, unfortunately), but will be in Midland Sunday night....
I have similar Jet and similar problem: mine only runs on high, no low or med speed; off-delay timers work fine; same output regardless of my inputs...