TO REPRODUCE

1) As admin go to Dashboard page
2) Add a block
3) Go to the block settings
4) On Select pages set ‘Any page matching the above’
5) Check block is displayed on My courses
6) Edit the block settings from within My courses page
7) Change the block settings setting "Select pages" to "This specific page"
8) The block disappear from Dashboard

The block can't be removed from the My courses page anymore, even if you make it visible again in the Dashboard, there are no options to remove it anymore

There are additional several questions here:

• Is it ok to add blocks to "My courses" via "Dashboard"
• Should not be the previous restricted to Site home and the option to display a block everywhere?