This is an usual bug, but I discovered if I create a macro that waits for someone to hold the tab key for a long period, that will break file name auto completion in the ZSH shell.
I started pulling my hair out, thinking I broke my shell configuration, but once I disable the Macro, everything worked.
From the Wiki:
So keep in mind that regardless of whether you trigger the macro on hot key pressed, down, released or tapped, the key is swallowed by the system and cannot be used for its normal purposes.
You'll find that an unmodified hot key trigger of any kind will prevent the key involved being passed to the frontmost app, which is why such are generally avoided.
Gotcha.. Still the greatest productivity tool that has ever existed.
Maybe this will save someone a few minutes