Not an answer, just sharing in case it helps. This is the thread with the issues I encountered when migrating to ic_cdk v0.18 crates.
Beyond one or two fixes within ic_cdk itself (are you using v0.18.5?), one of the main issues I ran into was resolved by enforcing all my spawned functions to use spawn_017_compat. The behavior of spawn was changed, which caused some features to trap.