error in GPS to track conversion

[girouette]

A friend has OpenCPN 4.1.1028 on a tablet running Android 4.0.3 with an ARM processor, and an internal GPS. The GPS gives the correct data, as checked with another GPS. The tracks show 2 kinds of errors:

1. The directions of the tracks are off by 160 to 240 degees to the correct ones.
2. The tracks show from time to time "jumps" exactly north-south or east-west. This displaced track is parallel to the original one. Either the tracks jump back after a minute or so, or might slowly drift back to the original track.

The speed given by the GPS is correct, while the speed seen on the tracks is also changing somewhat erratically.

What can be wrong? I assume an error in the GPS to track conversion.

girouette