I hate to say it, but if youre losing them at your current rate, you might be better off cutting your losses and going the slash and burn route.
New tubs, new substrate, new crickets...anything that touched the old colony cannot be put in contact with a new one without being sanitized. Densovirus (as a genus) have non-enveloped capsids, which generally means it survives longer outside of its host than other viruses. Starting everything over should theoretically stop the losses (assuming youre getting a clean supply of feeders)
Given how many different types of insects can get infected its likely that a lot of companies wont be able to clean themselves of this virus completely. A number of articles cited a rate of 9/10 inspected species from the order Lepidoptera to be carriers of CrPV (which might explain why the dubia's seem to be resistant), meaning all the companies that carry silk worms and horn worms have a potential source for the virus...and some articles even point to fruit flies as potential carriers