Transfer to Broadworks Network Directory Contacts - screen timeout issue

[livehappy42]

I am seeing issues in a particular Transfer condition.
Phones are T4x and T5x (as tested)
Running v86 FW
Broadworks Broadsoft

Issue:
During an active call, user wishes to transfer to a Network directory contact (Enterprise or Group)

Transfer > Directory (scroll thru directory)

The issue is that after 1-4 seconds the phone will revert from the directory back to the dialpad. This happens even if a user keeps their finger on the screen while scrolling. User does not have enough opportunity to find the contact they are looking for; this happens even when there are only ~20 contacts in the group/enterprise.

I have set the following in the config, with no effect:
account.1.dialplan.digitmap.interdigit_short_timer=30
account.1.dialplan.digitmap.interdigit_long_timer=60

Are there any other config parameters relating to the BW phonebook that would configure a timeout when attempting to transfer to a Directory contact?

*** Update- this seems to affect only touchscreen models in my testing (T48S/T57W) and did not affect T46S with those lovely physical buttons (all test phones still running v86)