I've joined rewrite projects towards the end a few times to try and steer them back on course, and the projects followed identical patterns - rewrite in shiny l

I've joined rewrite projects towards the end a few times to try and steer them back on course, and the projects followed identical patterns - rewrite in shiny latest language/architecture and get 80% of the way there, then get bogged down with a bunch of missed edge cases and obscure business logic that the existing application also learnt the hard way. Unless the existing system has terrible architecture and technical debt, or its written in some language where you can no longer find developers, be very weary of the "do it right this time" rewrite. Be double weary if no long term staff are still around with broad and deep business knowledge.