PrologException with SWI-v.8.x, jpl7, Repast simphony

I am seeing the following exception when running the simulation, with Java based Repast Simphony:

FATAL [Thread-10] 20:44:57,976 repast.simphony.ui.GUIScheduleRunner - RunTimeException when running the schedule
Current tick (2.0)
java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
	at repast.simphony.engine.schedule.DynamicTargetAction.execute(DynamicTargetAction.java:72)
	at repast.simphony.engine.controller.ScheduledMethodControllerAction$ScheduleMethodAllAction.execute(ScheduledMethodControllerAction.java:333)
	at repast.simphony.engine.schedule.DefaultAction.execute(DefaultAction.java:38)
	at repast.simphony.engine.schedule.ScheduleGroup.executeList(ScheduleGroup.java:205)
	at repast.simphony.engine.schedule.ScheduleGroup.execute(ScheduleGroup.java:231)
	at repast.simphony.engine.schedule.Schedule.execute(Schedule.java:352)
	at repast.simphony.ui.GUIScheduleRunner$ScheduleLoopRunnable.run(GUIScheduleRunner.java:52)
	at java.lang.Thread.run(Thread.java:821)
Caused by: java.lang.reflect.InvocationTargetException
	at caspPlainPlateauTeam.agents.CitizenAgent$$FastClassByCGLIB$$eeacca07.invoke(<generated>)
	at net.sf.cglib.reflect.FastMethod.invoke(FastMethod.java:53)
	at repast.simphony.engine.schedule.DynamicTargetAction.execute(DynamicTargetAction.java:69)
	... 7 more
Caused by: org.jpl7.PrologException: PrologException: error(type_error(free_of_attvar, ':'(user, stratum(_41, exp(_42, _43, _44, _45)))), context(':'(system, '/'('$tbl_variant_table', 6)), _46))
	at org.jpl7.Query.fetchNextSolution(Query.java:438)
	at org.jpl7.Query.hasMoreSolutions(Query.java:342)
	at org.jpl7.Query.oneSolution(Query.java:872)
	at caspPlainPlateauTeam.agents.CitizenAgent.choose_and_perform_action(CitizenAgent.java:283)
	at caspPlainPlateauTeam.agents.CitizenAgent.choose_strategy(CitizenAgent.java:209)
	... 10 more

I don’t recognise that type of Prolog error, but the code in question seems to work fine with SWI-v-7.x. I’m afraid that the Prolog code can’t be shared (I am a PhD student and the work is considered sensitive), but perhaps I can try to create a minimum working example for you, if that would be helpful.

Thanks,
Abira

I’d first look at this Prolog exception. Could be poor handling of the exception. Whether that is new or not, I can’t say. A small reproducible example can of course help.