New 645 music. First two kilometres missing from the map of all my runs

the map does not correlate and is only partial

Some fixes that could apply to your issue:

• Plug the watch into a computer
• Open the device hard drive
  • Windows: 
    
    • Open File Explorer
    • Click on This PC
    • Click on the Forerunner 645
  • Mac
    • Open Finder
    • Go to Computer
    • Click on the Garmin Drive
• Once in click on the Garmin Folder
• In the Garmin Folder delete the RemoteSW folder.
• Sync watch using Garmin Express
• Place device outdoors with a clear view of the sky for about 30 minutes.

Expired EPO on a Garmin Outdoor Watch

Looked at the EPO folder and it had updated about 10 minutes after my run. Not sure I fancy deleting it. I don't wear the watch. I bought it to wear while running so switch it on only a couple of minutes before I start running. Is that the problem? Is it taking several minutes outdoors to find its location. I don't want to wear the watch generally or have to prepare by switching it on (and leaving it outside) over half an hour before running!

Is that the problem? Is it taking several minutes outdoors to find its location.

That would be my guess. I understand the concern regarding deleting random files, but this is a common, well documented fix for your issue. Once the epo file is recreated, GPS acquisition will also be faster. You don't need to leave it out for 30 minutes all the time, just once, to fix possible GPS issues.

You need a fresh EPO (once a week or two). If the EPO is fresh, the acquiring of GPS satellites takes couple of seconds. To have a fresh EPO, you either have to sync the watch through the USB cable with Garmin Express, or you have to have a phone connected to the Internet (and to the watch) when you are starting the Activity - in that case it may take couple of seconds more (if the EPO file needs to be updated). Also it depends on the quality of the connection. A frequent problem is that people are still connected to their WiFi router, when stepping out of the door, and losing the connection as they move, while the EPO file is being downloaded - that then leads to problems with the GPS acquisition too.

Thanks for the replies. I will delete the current EPO and let it sync a new one. Then I think I'll try wearing the watch for an hour before running and also make sure I don't start my run until I'm several minutes away from home....Here's hoping!