question

Does your model have an Experimenter with a Variable that controls the "Number of Objects in Group"?

If so, then if you have a "default reset scenario" set, it will delete all but the first member of that group and then duplicate that object to the count specified in the table:

Also, you could have custom code calling destroyobject() or treenode.destroy() that is destroying the object. Without being able to replicate the issue, we can't tell you what is causing it.

to expand: closed without saving, reopened, operator assigned to group there, added another operator, did not assign it to a group, saved, hit reset, operator assigned to group disappeared, operator not assigned to group stayed where I put him. weird.

More info: this was a 19.0.0 model that was upgraded to 19.1.1. did not have this issue in 19.0.0. Do I have to rebuild this model from scratch in 19.1.1?? Tested on 3 models from 19.0.0 and they all do this.

I'm not able to replicate what you have described. I made a model in 19.0.4, added an operator to a group, then saved and opened in 19.1.1 and hit reset.

Perhaps if you update FlexSim 19.0.0 to 19.0.4 then it will add the operator to the group properly?

thanks, if i get one to replicate issue, I'll attach.