We have not heard from users about this and also could not reproduce from our side. The tif files (ortho or DSM) normally have floating data type and somes are too big to be opened by windows viewer. However, you should be able to open it in QGIS. If not, I would recommend you to write a support ticket to us using contact support at the top of this page. We will be glad to help.
You can also have a look at this post: Large Tif File - Mosiac - #3 by Greg_Campbell1