Camunda Error org.camunda.bpm.engine.ProcessEngineException: Unknown property used in expression

I am trying to use an delegate expression on a Service Task but throws this error “org.camunda.bpm.engine.ProcessEngineException: Unknown property used in expression ${aBCService.reminderEmailCheck(execution)}. Cause Cannot resolve identifier ‘aBCService’”

We tried with enabling “Asynchronous Before” and “Exclusive” settings on the timer but didn’t work. We put a 5 sec timer after the “Start 2 day Reminder” Timer but still did not work. We tried with the combination of approach#1 and #2 but still did not work.

The timer “Start 2 Day Reminder” fails at least 80-90% of the times. The delegate “aBCService” is being referred at many places in the process but it doesn’t fail anywhere else. It fails only while using in combination with timer in the process. Anything wrong while referring a bean just after a timer in process ?