This is just a quick post of a solution to my issue. I have an early 04 F250. Built April of 04. Has the old style HPOP however every other component of the vehicle is 04 parts. Anyway I was getting to described above symptoms and this is what I did... I drained and refilled the trans oil(Mercon SP), replaced both trans filters, replaced brake switch, FPR(Due to a leak) and test all transmission solenoids for proper resistance. All solenoids checked out with perfect OMS. Last I tested the FICM-low voltage. I wasn’t sure what was causing the issue still... no sign of the torque converter going bad. Fluid in the pan and filters looked, smelled and felt great. I knew the FICM had connection to the transmission but I could not find the details I was looking for. I was getting sluggish throttle response and due to the low voltage already found I bit the $659 and replaced it. As soon as I did I had no more delayed shifts , hard engagements into reverse and drive or any slipping as I drove. Not saying this will fix any of the listed symptoms because I don’t fully understand the connection Bettye FICM and Transmission but it cured mine. Hope this helps someone out there that is trying to diagnose.

Very true on the batteries and alternator. I had a weak battery awhile back as well as an alternator. I fixed those about 8 months ago. No issues with either sense then. It could have caused and issue with the FICM then...