1. I am having a similiar problem, but for a Progress Mission, not for a Clan Mission.
I got the pop-up that said I had completed the mission, and the bubble announcing this also appeared above the Progess Mission icon on the home page. However when I open the Progress Mission icon, it has remained stuck now for 5 days.
See the attached pics showing this.
2. Also, as soon as I sent this info in as a bug report, I got a message that I was now baned for two days because of spamming. I never spammed, just played the game and sent a messge to the bug investigator.
Data on my environment:
Is occuring on both my devices:
iPhone 11, iOS 16.2
Lenovo Ideapad 5 14/AL7 laptop with Windows 11 -22H2 Home.
12th Gen Intel(R) Core(TM) i5-1235U 1.30 GHz, 16 GB
Steps I performed in the game before the issue occurred:
Was repeatedly playing Sewers of Arnac stage 4 and trying to reach the award of "Gauntlets with ATK (%) as the primary stat from Stage 4...", per the Mission statement.
Afterward I completed the requirement for the Mission award three additional times. Contition persisted. Rebooted laptop and phone. No change.