Part of one track missing

Because there is a limit on the number of track and route points that your Etrex will display. If you send a track or route over the limit they will be truncated.

Thanks for your reply, I have split the track and it is showing all. 
Is there any way of knowing that limit?
Also if you are approaching that limit would this cause the unit to freeze or just be buggy?

Nothing happens, once you reach the limit the track or route will end. 

For routes on your device the point limit is 50 if using the 'on road' setting, and 250 if using the 'off road' setting.

For tracks the limit is 10,000 points.

Sorry no idea why it was still freezing but glad all is now ok.

I've prepped for this when on a super-long trip with my 64st, saving track portions on occasion before getting near the limit. On my unit, I seem to recall that it is the points at the beginning of the track that will disappear as new points are recorded at more recent positions. I have always been able to later join the pieces into one track, if desired, in BaseCamp.

Thanks for your help.

This was a track, that I had made using Google earth Pro, then converted to GPX. The track was to long as Sassamb said. I used basecamp to break down into small sections and all tracks are on SD card. 

The easiest way to limit the track points being sent to a device. is to change a setting in Basecamp Preferences.  I do this for my GPSMap 60csx and have it set to 500  The following is from the Basecamp Docs.

Setting Data Transfer Preferences
You can customize how route and track data is sent to specific devices. The BaseCamp' application remembers
devices you have previously connected, and you can set preferences without connecting a previously connected
device.
1. Select BaseCamp > Preferences > Transfer.
2. Select a device.
3
Select one or more options:
To reduce the detail of routes by removing points from the routes when they are transferred to the device,
select Strip shaping points from routes on transfer to device.
• To match the routes to the internal maps of the device when they are transferred, select Always match the
route to the map on my device when transferring.
• To limit the detail level of tracks sent to the device, select Simplify tracks by removing intermediate points,
and enter the maximum number of points per track.

daknudsen

Yes, that's a different behaviour as you're talking about recording a track on your device. That does work by deleting older points once you reach the 10,000 point track limit.