Hello,
It has been awhile and my memory may be hazy, but this is unlikely what happened in either case. In the former, all units, even those not near any mage stopped responding to attack commands and I was unable to stop or damage that last wave at all, any unit. They slow walked to the end as if my team was not present. In the case of the immortal mob, this is also unlikely as I had sent two mobs, both firing projectiles and the mage could not be damaged at all. Unfortunately, I do not remember if I was able to find a way to damage it or had to restart. I believe I had to restart because I know I never passed that 5th wave, with my first attempt there being my army not attacking and I believe the second with the immortal mage. At that point, I thought it was an artificial barrier to progressing further.
Thanks!