Sorry for our late reply.
Concerning the issue you mentioned, is this project created in Twinmotion 2018 and opened in Twinmotion 2019, or it is created directly in Twinmotion 2019? Does this happen all the time and inside Twinmotion viewport or in a rendering?
It would be the best if you could send us your Twinmotion file via Abvent support ticket
so we can test it further. Please give us some details about the above questions in the ticket too!