I cannot find any specific causation, but any redstone signal traveling by repeater across a chunk border runs the risk of not being loaded. In this case, I have the entire checkered board floor space inside a tickingarea, so the chunks should be loaded. The repeaters suddenly act like they don't exist and refuse a signal, and all additional repeaters in that chunk seem to do the same. 

https://youtu.be/xXGWKmNllO8