Hi ,
This sounds like it might be a bug. Could you please submit a bug report here and share a copy of your files so our support team can investigate this? We would need a copy of the Twinmotion file packaged using the Resource Collector in Twinmotion (Edit menu > Resource Collector > Compress files) and if you are using any custom materials, we will need the .TMI files for the materials.
Best,
Raghib