This is a process that I've always used. First I call the bulk data from model derivative for further structuring. But this time the derivative data is confusing. Because when I use getProperties from viewer it shows external id with expected format(0/0/0/145/79) but when the same element is called from derivative api, on the field of external id, ifcGUID (11h5ts$FhghhDGbOs) is written.
In short I can not get external id of element from derivative Api but it can be found from viewer. What could cause to such confusion ?
Today I have uploaded the model with SVF format instead of SVF2 and it looks like everything is working fine and as expected. But I think this topic needs further investigation.