Regarding the map shift issue, I once had a shift of approximately five miles after about as many hours airborne.
On non-GPS a/c B757 (similar system to a classic) I had 1.5nm map shift landing in Azores, and also into Cairo coming up from Mombasa. That was scary as it was a VOR approach on the easterly northern runway in a sand storm. The magenta line was line up on the southerly runway. When we flew through the m.g. in HDG SEL and VOR/LOC armed there was scrambling to check we had the correct frequency dialled in. We had, but it was a moment of ?????
I've found the common split of ND displays to be PM on raw data & PF on Map.