I have located an old beta firmware for the A129, V1.11 from May 2018. I ran this on my A129 camera this morning and found no duplicate frames on the rear camera.
Note that I use my A129 as a side-facing dashcam, so the rear camera is looking to the left.
Original file :
A129 Rear Camera - FW V1.11
If anyone else wants to test this FW on their camera it will be available
HERE for a short duration.
IMPORTANT: This is beta FW for testing only. Please do not use it for regular driving.
I do not know what changed between V1.11 and V1.2 that introduced the duplicate frames. I will leave this with Viofo to address in their own time. I'm restoring my A129 to FW V1.9.