MechJeb version: 2.14.3.0-1412
Mods: RP-1 express install, including mods listed by CKAN as recommended
Ship: Thor-Agena 2 Magnetometry.zip

I have a design that has a long coast and then an apogee kick stage, but it spins up in the middle of the pre-coast burn, I guess because the ascent is vertical enough that mechjeb thinks it isn't trying to steer. Here are my launch settings:

If you want to reproduce it, you'll have to coax it into finding a path by starting at an apoapsis of 3050 and slowly increasing it. Usually I go 3050->4000->6000->10000->100000. I have gotten this issue on other designs before, but only when I set physics time warp to 4x, so I was hoping that I could just work around by not warping during the pre-coast burn. Unfortunately that didn't help in this case.

Maybe the lead time should be used to prevent spinning until that amount of time is left before the next stage? Then you could also allow disabling the turning check, which could be used to spin up without a coast like you used to be able to. I looked at the code and it seems like the lead time is not used anywhere, which is strange since it is still in the menu.

Also, a related issue is that if you try to use the first stage of a vehicle to spin up, it will start spinning during the initial climb. This means that you can't make a Juno I-like design that only has guidance on the booster stage (actually, Juno I would separate the booster from the attitude thrusters, and then separate those after coasting, but I don't know whether that works with the autostage and coast features of MechJeb).