CRM migrators/implementers/trainers: have you ever had a client come to you to move away from their own custom-coded CRM and migrate over to the platform you work with ?

Bonus question: what was the breaking point that made them realize coding their own system was a mistake ?

I'm here to read you, be the shoulder to cry on, or laugh if it's been long enough, as I've never personally done this before, so I have no story to share, but I've been thinking about what migrating to a new CRM could be like.