F28069U: Flashing with UniFlash fails

Hello,
When I flash F28069U device with UniFlash (v3.1.0), I get the following errors:
==============
[15:51:24] ERROR >> C28xx: Flash operation timed out waiting for the algorithm to complete. Operation cancelled.
[15:51:24] ERROR >> C28xx: GEL: File: c:\MCU1_C4.0.00.out: Load failed.
[15:51:24] File: c:\MCU1_C4.0.00.out: Load failed.
[15:51:25] Loading program: c:\BOOTMCU1_C4.0.00.out
[15:51:45] ERROR >> C28xx: Flash Programmer: Error encountered when writing to flash memory
[15:51:46] ERROR >> C28xx: GEL: File: c:\BOOTMCU1_C4.0.00.out: Load failed.
[15:51:46] File: c:\BOOTMCU1_C4.0.00.out: Load failed.
[15:51:46] Programs operation finished.
================

However, if I change the PLLCR value in UniFlash from 18 to 16, it flashes without error.
These are the settings of UniFlash
OSCCLK (MHz):   10
CLKINDIV:       2
PLLCR Value:    18
[CSM Passwords are all 0xFFFF and there was no power loss or any other interruptions during Erase, that might lead to CSM Lock]

The issue is that chaning from 18 to 16 is not starighforward. The *.uniflashsession file has to be modified and this doesn't work
if I want automation of this (e.g., End of Line programming).

I searched in the web and didn't get help on this topic.
Does anyone know how do I change the PLLCR value from 18 to 16?

thank you!
--
Vishwanatha