I think there may be a bug on script editor. Following this steps i can reproduce the bug (using the terminal's comand line by winbox). Please take a look:
1) Create some script. Example: /system script add name=test-script
2) Edit this script by running: /system script edit test-script source
3) Add some content. It could be just comments, but one line must be greather in size than the window of the script editor.
Taking as example this content:
If the first line has not fit in the window you should see a ">" character on the end of visible part.# This should be a coment line who's size is greather than the window of the script editor, meaning, you can not saw all this text on the editor.
# some other short text that fits in the line.
4) Now save and exit the script editor by pressing CRTL+o
5) Reopen the script for editing: /system script edit test-script source
6) Go to the end of the last line (the short one), and start to erase everything with backspace.
As the cursor moves from the second line to the end of the first line the CPU goes to 100% and the script editor stops working. Nothing else can be done on this window, but the rest
continues working well.
7) Take look at Tools/profile. You will see a console process using a lot of CPU. This is not normal.
8 ) Now close the script editor's window and try to open a new terminal. You will see that no command line will be presented.
The only way I found to recover the command line was reboot the hardware.
I tried this steps on RB750Gr3, CCR1009 and some other models. The RouterOS versions were above 6.43.4. But also saw this in older versions.
I am hope some one could confirm this.