attach the screenshots of your blocks.
There is no timer set therefore the app cannot stop any timers and the error occurs… Please check the flow of your app to make sure you start a timer before stopping it.
From the error message I would also think that. But though there is no Timer component in KodularC, maybe a Clock misbehaves.
What are your blocks related to clocks?
Remove all your timers from a backup version and tell us if the error sill showing.