Hello Chris,
sorry for the late-ish reply.
I am unable to reproduce this issue on my side. Would it be possible to send over a scene and textures, with steps to reproduce?
Also does this happen if you choose to store them with the scene? (in a tex folder next to the .c4d file)
As usual, versions of corona and c4d are always helpful to disclose.
Thanks,
Jan
EDIT:
I just somehow managed to encounter the issue, even with a bit different approach. Will investigate and then report to the devs. Thank you for reporting!