Signal loss over time

I have 2 runs with 4 strips on each. Each run has roughly 500-600 LEDs. On my farther run I’ve used a sacrificial pixel to get the signal correctly to the farther run, not perfect, but it works for now. When I turn on certian effects and leave it on, after about 40 min/1 hour the farther run gets messed up. The first strip of 4 still works no problem. The next 3 strips all stay red. Even when I turn them off they stay red. I have to unplug the power to have them turn off. If I turn it right back on, the last 3 strips are still red. After some time I can turn it back on with no issues again. I’m at a loss on where to start troubleshooting.

What’s the distance from the MCU to the sacrificial pixel and from there to the strip?
How are you powering the MCU, does it have it’s own power supply (or cable from the main PSU) or is the power coming “back” from the powered up strip?

When the strips turn red, can you still control the MCU?
Have you tried dropping the master brightness to see if things last longer?
What version of WLED are you running?