A thought (I too had problems with SerialManager1.1, but got it to work
once when I experimented; never did anything real serious with it yet
though):
Are you setting the 'SetCRMode ON', which will send a CR at the end of each
SEND? Otherwise you will need to append a CR to each message. If I recall
even this was not 100%. I think the way I got much better results was by
sending character after character, rather than whole lines. (ie.
SetBufferSize, SetByteMode)
If you are still having problems I will try to find my deck that
experimented with it for you…. –jp–