When using Excel 2016, and copying a cell, NOT the text inside it, but instead the cell itself, Clipboard Fusion is doing something causing focus to be stolen, preventing from pasting at a later time.
I know it's ClipboardFusion as if I shut down the application, I immediately see the behavior stop.
I reproduced the issue, and logged and am attaching the log file in CSV format for you. You should see the message it is pressing Esc.
• Attachment [protected]: ExcelBug_ClipboardFusion.csv [4,754 bytes]
On the ClipboardFusion Settings > Options tab, do you have the "Automatically press escape after copying from Microsoft Excel" option enabled?