For the first issue, this error was reported in the main campaign if community mods were in use, Larian mods enabled and then some of the community mods disabled.
For the second, one person reported this entering Reaper's Coast, and a couple with the act transition to the Nameless Isle, in at least one case due to having some mods disabled that were previously used (that happened in single player, though).
QA is currently investigating a similar report in the main campaign, in multiplayer (not using Helaene's mods, but with OdinBlade's class mods and a couple others, so that type of mod may be the issue), just requiring a save/load on the tutorial boat to get a hanging loading screen entering Fort Joy.
