Will I run another instance of the job if it is already running?

[roman042]

Hello, tell me if another instance of the job (ScheduledJob) will be started, if it is still running?

[tarasm]

After 2 hours this ScheduledJob will be marked as Failed and will run again. If the job has the running status every time after execution, this can notify about fatal error in the code. Is this your custom code?

[roman042]

Yes.
Tell me what are the recommendations for writing a job?

[tarasm]

You have to find the error. If you're using PHP 7+, the error should be stored in the log file (/data/logs/). If PHP 5, you have to run crobjob command manually via terminal.