1. Please describe as detailed as possible what you did and which problem that leads to.
On Map Editor, while, scrolling, either with the scroll bar, or with the mouse, the thumbnail disapears, and reappears, etc... 
Just look: https://streamable.com/tqjtj
But, not in big thumb, in large thumbs, it works 
2. Please post your logfile and if possible attach your debug logfile, as well, which have been created during the problem occured.
3. If it is a performance or another possibly hardware-related problem, please post your system information. Those are:
- OS and architecture (32/64bit): 64 bit
- Processor clock rate: 3.5Ghz
- Processor cores: 4
- RAM: 8 GB
- Type of hard drive (HDD/SDD): SSD, but LOTUS is on HHD
- Desktop or Notebook? Desktop
- Name of your graphics card: GTX 970
- Graphics memory: 4 GB
- GPU clock rate: 1140MHz
- OpenGL version (see LOTUS logfile): 4.6.0 NVIDIA 416.34