Testing out a P12s. String of 96 on port 1 in test mode works as expected. String 2 has 128 pixels. In test mode all it does is flash every few seconds. Any ideas on what causes it to flash quickly in test mode?
I have had that happen to me before. In my case it seemed to occur quite randomly in different strips that ran properly in test mode sometimes and flashed at other times.
All I would do is turn off test mode in the P12s settings, click reboot, then try test mode again and often the flashing was gone and normal test pattern occurred. Never figured out why it happened but was alway relieved to see it go.