>>What exception handling do you have in the method? - you should be able to catch it there before TargetInvocationException kicks in.
>
>This is the framework generic error handling that has been there for years. Only in this mode I started to have problems.

So wrap the code that calls Invoke() (Framework.Robot.ProcessTaskQuery() ?) in a try/catch and, assuming the exception type is TargetInvocationException, write the inner exception to the log.

>>Also, since this is intermittent, is it possible that a previous call to the method had not completed before the timer fired again?
>>If that's a possiblility you will need to ensure that your code is re-entrant....
>
>Once a timer fires, the timer is shut down during the process. It can only be enabled back once the processed is completed.