Brake Lights on, then off 1998 K 1500

I have a 1998K 1500 that have a weird brake light problem. The brake lights
come on with the pedal pressed in 1/4 and stay on if you leave the pedal
here, any further in and they go out. You can actually hear the relay in the
fuse box click on and then click out as soon as you press it further. I replaced
the brake switch ( difficult and only fits 1 way) ) and the relay, Same thing. All
lights are fine in a small range of pedal pressing. Since everything works in
the limited range of pedal movement I can't see it being the turn switch. Also
the flashers work correctly and stop flashing in the small range of pedal
action, but restart flashing as you push the pedal in further. Any ideas. There
was a post like this before but no solutions.