I realy dont know, but have sent a email to Telldus and asked about it. It is possible that it is because some off the switches from Nexa are old ones. I use Switch King as a standard controller. It is very good and there you can repeat the signal how many times you like.
Bye the way! Thanks for a realy good software!
That tends to happen if you use a too short hex transmission (normally need to send it 3 times then). I am not sure how the tellstick stores the different hex signals or what format it even uses, tell me what nexa switches you have and I might have the proper hex commands for you that don't ever need repeated sending.