I went through some of the Tomb of Annihilation module a few months ago. Due to someone throwing a tantrum (certain things he was saying was true in certain ways, but the way he said it was terrible), the Dungeon Master lost her will to continue; things got awkward in the group and we scattered. I am starting the module once more with the same DM but with different players, and I am scared that a similar thing may occur.
The last player's most prominent complaint was that the Dungeon Master was sometimes late (around 1 out of 4 times). He also stated that he felt like he wasn't being catered to, as usually the DM in question runs groups with 6 or more people, and sometimes you have to wait for your turn to actually get something done.
As far as I could tell, the rest of the group didn't have problems with the DM being late and not having enough attention as it were.
If someone states complaints similar to this in a dramatic manner, how can I prevent the group from feeling too depressed to continue and cheer up the Dungeon Master?