Using v18.1, we had an issue where selecting cells using the shift and down keys, and then while continuing to hold the shift key hit the left key, results in an ArgumentException.  It seems to only happen when there is a row with merged cells in the middle.

Attached is a dummy project that loads a .xlsx file.  It can be reproduced by selecting cell A108 with the mouse, then holding the shift key and selecting down to A115 with the down arrow key, and without lifting the shift key press the left arrow key.

XamSpreadsheetShiftLeft.zip