Everyone is right, it is a memory thing. From what I can tell, it's easy to fill up the memory on a M1225 with programming and reprogramming.
Try this. Clear out the memory completely. Delete all the channels and the alpha tags. Start fresh. Add each channel as you want it but without alpha tags. Only use Rx PL when absolutely necessary. Only program other features if essential. You should be able to get your half duplex channels with talk-around programmed correctly.
With the channels all programmed, you should be able to go back and add alpha tags. Keep them as short and simple as you can because every character uses more memory, even spaces. For example, instead of Fire Channel 1, just program FIRE1 and so on.
Please DO NOT email or PM me with general technical questions. They should be posted on the forum.
Let everyone have the chance to respond and to see each others' answers.