InnoDB cannot find a row - possible index corruption?
looking for Your data - Your columns is VARCHAR, but not date, this is make query non working with any non readable character in data

by run UPDATES:

UPDATE mytable SET Start='2018-02-04 11:31' where id=1;
UPDATE mytable SET Start='2018-02-04 11:30' where id=1;


You are fix this situation

Proper way for work with dates - have datetime type for date time columns

in this case Your data would look like:

+----+---------------------+---------------------+
| Id |      Start          |       End           |
+----+---------------------+---------------------+
|  1 | 2018-02-04 11:30:00 | 2018-02-05 12:00:00 |
|  2 | 2018-02-04 15:40:00 | 2018-02-05 08:00:00 |
|  3 | 2018-02-05 10:00:00 | 2018-02-06 09:00:00 |