Wow, very strange. This is a new one to me personally. Haven’t seen anyone report this one before.
To summarize your issue; You do NOT have this issue normally with Ark, or within the Dev Kit. You can play Ark normally, and run the Dev Kit normally. Only with your custom map after having cooked it does this problem occur?
A few things I’m contemplating as possibilities (odd ones);
Did you add too many global light sources? I HIGHLY doubt this is it at all, but I could see this destroying GPU cycles big time.
By weather, do you mean custom added weather by you? If so, is this using GPU particle emitters? If so, again can see this ruining GPU cycles if not done right, or if it’s using a bad Event or boolean (Example; Event on tick, with unspecified time set for the tick) that is causing that. Another very doubtful possibility I want to throw out there just in case.
Is there ANY custom content outside of the Dev Kit added in on the map? If so would you mind sharing what? I’m wondering if possibly a bad asset could cause this behavior? Very doubtful yet again >.<
Not really sure about any of these, just throwing a few thoughts that came to mind