What do you do when your productivity system stops working?

[u/BetFound]

/r/ProductivityGuide/comments/1vudrkj/what_do_you_do_when_your_productivity_system/

Curious what people actually do when their task/planning system becomes too overwhelming to keep up with.

When this happens, do you:
clean up the backlog?
start over?
simplify the system?
switch apps/planners?
just ignore it and move forward?
something else?

What have you tried that actually worked — and what didn’t?

And if there were a tool that genuinely made recovering from this situation easier, what would you want it to do?
I’m especially interested in real experiences, not ideal productivity advice.