I installed a UC520 at a customer about a month ago.  They are using all SPA525G sets, including the receptionist.  She has two add-on modules.

Her button layout is below:

Phone                                                   1^st module

X300 (her ext)                                        Line 1

X252                                                      Line 2

X251                                                      Line 3

X260                                                      Line 4

X 301                                                     Line 5   

                                                              Line 6

                                                              Line 7

                                                              Line 8

                                                                X

                                                                X

                                                                X

                                                                X

                                                                X

                                                                ETC,,,,

The rest of the keys on the add-on modules are extensions…

Call comes in, it rings to Line 1 (line2,line3,etc…).  She transfers it.  All is well.

Call comes in, she answers it.  Before she can transfer it, another call comes in.  Her Transfer softkey disappears.  She can’t do anything with the call.  The 2^nd call goes unanswered at her phone and rolls to a back up person where it is answered.

She is very frustrated.  I don’t know if it is so much of a software issue.  I think I either have it programmed way to weird (with the keys on the add-on) or she needs a different phone type (7931?)  Thoughts?  Suggestions?