A bug in the CAS

[Freire]

I believe It's because of CAS precision that would go only to 12 decimal places, if you try to do math with 1E-11 it works, bellow 1E-11 it doesn't [1E-12 for example - starts to repeat] remember that also CAS may not return exact values.
This kind of math should be handled by Home view, on Home view everything works as expected.