Broken or damaged bottom screeens are sadly too common. Many companies have tried to save a few dollars by using less expensive bottom screens. Some low quality screens can cost 1/10th as much as a high quality screen. Many companies have switched over to the Fleck bottom screens to eliminate this as being a problem. The 40922 and 40924 screens are extremely expensive compared to some of the low end bottom screens, but it also virtually eliminates this problem in the future. These screens are also the highest flowing screens as well as being a fine mesh design. There are many other high quality screens available, but I have yet to find one as good as the 40922. The biggest issue in the past decade has been the "knock-offs" that look like a reputable companies bottom screen, but in testing, they fail miserably. Also, many companies do not use a gravel underbed. Gravel underbedding is always recommended unless you have a vortech tank design.
Jims advice on clearing the plumbing is perfect. It is difficult and time consuming clearing resin from a plumbing system. I would add that you should open the bottom of the water heater (annual flushing is recommended anyway), if resin is in the bottom of the water heater, you may have considerable difficulty getting it all out. Repeated flushes will help.