DigiLite Config is written in Visual Basic and it uses the Windows regional settings to decide how to show decimals. The symbol rate for SR 4167 is actually 4166.66666 and where "," is used in decimals, this value is written to the Windows registry as "4166,66666" .
DigiLite Transmit is written in Borland C5.5 and it appears to always use "." for decimals, irrespective of the Windows regional settings. When it tries to round up the symbol rate, it sees "4166,66666" and stops at the comma, which it doesn't expect in a number and comes up with the answer 4166. This is the value sent to the serialiser. The serialiser doesn't know how to handle SR4166 and flashes in threes.
The solution for xx67 symbol rates is to put the value into DigiLite Config with a "." by holding CTRL and hitting U to display the 'User Symbol Rate Settings' box and then entering the symbol rate as xx66.66666 even if you normally use "," for decimals.