[Crash] Plugin crashes when inserting item into Hash Map (process function) about nih-plug HOT 1 CLOSED

You've enabled the assert_process_allocs feature and you're allocating on the audio thread. Enabling this feature will cause all audio thread allocations to panic. You should avoid allocating on the audio thread, as allocations may stall the program for an undetermined amount of time. In general you'll want to avoid any operation that doesn't have a known upper runtime limit on audio threads (anything that isn't wait-free, although lock-free algorithms are almost always perfectly fine if there's not a ton of congestion). So that excludes, (de)allocations, file operations, mutexes, and most system calls.

from nih-plug.