thanks for question and detailed explanation.
As you say it doesn't seem to be a specific unit issue.
1, Lets check firmware first
we haven't updated the firmware for a while, but its worth checking what your using and updating if needed.
please see attached pic - firmware version is shown on power up
please confirm its V3.20 on both your units.
IF it is < 3.20 please get latest from
Zip file contains instructions and it only takes 15 mins using AT EDITOR.
2, As you say other programs are ok, just not "this one"
Can you send a copy of the ATP test program in please so we can check it here?
Please reply to this thread and attach, or just email it into firstname.lastname@example.org