When using angular 18 with Standalone architecture (following most recent default way of installing angular, in their docs), the animations from toast will not run for the flyIn part (fade-in). The animations on flyOut (fade-out) work fine.
This is because of provideZoneChangeDetection({ eventCoalescing: true }), this configuration comes from the default angular installation.
Here's an image where I open all of these toasts, notice how only some of them are running the fade-in animation:

I don't know what are the criteria for the flyIn animation to trigger, but the first toast always works
Here's an image where they're all closing, at the same time without any issue:

Here's a StackBlitz example, with provideZoneChangeDetection({ eventCoalescing: true }):
https://stackblitz.com/edit/stackblitz-starters-c2dgtr?file=src%2Fapp%2Fapp.config.ts
To disable this config, go to src/app/app.config.ts and remove it, or remove all parameters being passed into the method.
I do not know what are the effects of disabling provideZoneChangeDetection, but I'm pretty sure this is a bug within ngx-toastr, since the flyOut animation works as expected