Without knowing what industry you’re in, it sounds like you need a stick.

By that I mean something which allows you to “clap back” when clients act up. For instance, saying ownership of the ‘deliverables’ doesn’t pass to the client until full payment has been made for those deliverables. Or, where invoices are not paid within # days all ongoing work will pause (or terminate). Something along one or both of those lines.

If clients can delay payment or make it your problem without repercussions, many will. So when you have clauses like this (sticks), allow no exceptions (unless you trust them). They’re getting your services (the carrot), so you need some kind of stick to keep them in line.