Hi. One known issue is that switching between NM and UNM may set off the counter.

However that is not the case here. Just a bug. Either write a ticket to a support, or send me your UID in direct message so I can forward your issue.

i've tried the ticket, but it props an empty message warning when I'm adding the image and it doesn't send...

I'll message you the ID them

tks

Have you managed to solve your issue yet? It needs to be done through ticket exclusively.

There are only 2 known causes for this problem, the first one you have already mentioned (make boss change). The second is that there has been a restart of daily missions or boss, that can also cause that problem.

If the problem is not any of these and it persists, send us your id privately to notify the developers

i've only attacked the NM, and completed before the resart

No ideia if it would persist, as i've completed the mission. Simply had to use 2 extra keys :(

Ive had the same thing happen to me yesterday...have screenshot of 106 million damage done to NM clan boss, however, support is not being very "supportive" with this issue. 

Anyone like to help with this?

Only support can "manipulate" account. Did you write a ticket, elaborated your issue while providing proof and your UID?