It's always annoying when your baby monitor has lost connection. This can have several causes, such as concrete floors with steel reinforcements, well insulated houses, refrigerators, microwaves etc. You can try the following to improve the connection: 

• Deregister the baby monitors and re-register the baby monitors according to the instructions in the manual. When doing so, try to leave the baby unit in the baby's room and the parent unit in the place where you want to watch. When logging on. It is possible that you have to learn this with 2 persons. 
• The DVM-64 works on 2,4Ghz, your home wifi is also on this frequency. It is possible that they interfere with each other. You can check this by unplugging the modem and see if the connection has improved. If this is the case, you can set your modem's wifi to a different channel. How to do this can be found in the manual of your modem.
• To make sure that you do not have a disturbing factor in your home, you can try your baby monitor at someone else's house (not at the neighbours') to see if it works there.