It's really situational. Does not have to be in detail or length. Something along the lines "hey, we know we have these issues, they are being worked on" and even regular updates saying "we are still working on it". When it goes dark, some people get antsy.
When I fix something that impacts my clients I contact them (email, phone, etc) or have another team member do it. They feel much better knowing we are working on it and keeping them updated. While it's not an apples to apples comparison I still feel it applies in some fashion.