If you take a change to read through some already posted threads, some of this has been posted. I will share with a summary-
It has been a combination of things, some server issues, Steam API/Network, ARK updates, and mods. Everyone's issue is different.
For a crashstack, the only fix is rolling back to a save that works. No way of knowing which one will work until you roll back.
Most of the issues listed is about 3 days. But prior and even now can be the mods. Until the DevKit is released, mods typically wont be updated. So mods as always are at a risk and best effort. No one can really tell you all the combinations out there that may or may not work. Just practice basic things like, dont use 2 yellow mods. Workshops explain more about that is 'stacking'.
I suspect the ticket queue is busy atm. Typically it is 24-48hrs weekdays, and when busy upwards to 72hrs- 5 days.
We just ask folks to be patience please. Much of this can not be controlled by Nitrado.