GPS is not affected by poleshifts.
your electronic maps might have to be updated though on magnetic deviation for same reason.
two very different things.
solar activity will have an effect on satellites that make up GPS system among other things, also comms with said satellites may be hampered. Under solar activity one should understand that also a lack of solar activity is significant in that it weakens the magnetosphere and the protection against cosmic rays that gives us is also weakened.
This phenomenon is due to persist for many more years and to even increase.
Errors in GPS location are normal in every time of conflict as the military will want to render its use by opponents ineffectual. I witnessed this firsthand during several occasions in the past.
Keep situational awareness at all times.