Most problems like this are poor power supply. First thing to do is try another new set of batteries, you would not be the first person to get faulty batteries out of a packet.
(do you have a multi meter to test them?) Then: Are the battery terminals clean and corrosion free, this is often a problem when batteries have leaked in the remote. In some cases I have seen leaked batteries corrode the device's terminal badly enough the terminals need to be re-manufactured. Check the terminal are reaching the battery surfaces with a bit of tension on them. Some batteries have flatter terminals so the device's contacts don't reach them solidly. You may be able to use tweezers or similar to stretch the device's terminals.