Description
Once the cells are merged using the Ctrl+M keyboard shortcut the cell won't be toggled to the unmerged state. The issue is happening only when the table is rendered in RTL mode.
LTR:

RTL (bug):

Demo
https://jsfiddle.net/budnix/2zsrp89h/
Your environment
- Handsontable version:
develop
- Browser name and version: any
- Operating system: any