signal strength and vcr recording


We are able to get fairly good DTV reception for days, then out of the blue will have trouble with the channel strength, loosing the whole channel for time periods. Completely on accident we discovered that the channel can be unwatchable on TV, but if we are recording it with the VCR, can watch it later, no problems. What is going on? It seems to me that if the VCR can record it, we should be able to watch it. What are we missing?