It is observed that a timer set to run monthly in previous years, stops executing in the new year.
The settings are similar to the below:
Every 1 Month
Starting in August
The monthly timers that start on a particular month will only execute from that month forward.
Meaning, August 2018 will run through December. Come January it will reset and not run again until the specified month.
A look at the execution schedule will reveal the below: