Speculating a bit, taking Bindooks 14.7 nm south.
If we look at:
Spherical geometry
Data storage
Software functions
The usual method of handling angles as in lat is from the N pole in radians and a convenient way of storing it would be 3 bytes in microradians
For BLAED at ~ S36:29 this would be 126.48 deg or &H21AF3E uradian, the A would be 1010 in binary. Flip one bit to 1011 to get B and we have &H21BF3E which translates to ~ S36:43.
Without knowing exactly how the GPS storage and calculation all works internally it is difficult to say but this change could occur either in the card or in intermeadiate (RAM, EEPROM or Flash) storage for the leg. As to what could flip the bit the current size/charge of bit storage these days means cosmic rays or radioactive decay on an atom within the chip/packaging can do it.
An interesting exercise for ASTB.