I know this is an old thread but I had the same issue and resolved it as follows.
Modified the "On Modifiy Script" for each field. See below
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local inst = mc.mcGetInstance()
-- Commented out GetProperty
-- local val = scr.GetProperty("droCalZ", "Value")
-- add select to get the user supplied value.
local val = select(1,...) -- Get the user supplied value.
mc.mcProfileWriteString(inst, "PersistentDROs", "droCalZ", string.format (val)) --Create a register and write to it
-- added the return at end.
return val
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This solution came from topic=47662.0