I have never had a problem with electrical trims with the slave following the master. Don't have any idea what fmo code would be, may want to call Futaba/Hobby Services on that one. Anyway, after I do my initial trim flight, I go back and readjust the trims mechanically, so the radio is centered on the trims, then do it again until all is neutral.

You may want to check your sub trims to make sure there is nothing in there that shouldn't be. I don't believe in subtrims. Make sure your ATV or end point adjustments are all at 100% for both the masters and the slaves, then if you need or want more throw, use dual rate adjustments to increase anything you want. Also, check all of your mixes to make sure there isn't something being done that you don't want done. Some times you may need to reset it all and start over, to make sure you don't have a mix in you don't want. I usually make notes in my model manual as I go, so I can refer back to what I did, should I have a problem. I have some planes using all 8 channels, with Crow and a bunch of mixes, so it can get messed up really fast if you don't keep track of what you have done.
Kind of hard to give anymore info, without having your radio in my hands.
hope this helps, happy landings.