That the INS degrades is a well known fact. Heatblur introduced it almost one year ago in their post called “All About Inertia“. I soon realized that re-aligning the INS while the ground crew rearms and refuels the aircraft is very important to ensure proper navigation and both AA and AG efficiency. Whilst-R&R complete re-alignment, plus a occasional TACAN fix, solve most issues. Usually.. Yesterday we were conducting some AG tests but my pilot had massive lag spikes due to his streaming acting weirdly.
This is a screenshot from TacView:
What I did not expect is that the movement induced by the latency somehow affects the INS! I still do not understand why since only the RIO was rubber-banding (myself) and not the pilot. Nevertheless, I created the HB WP right over AF and after this short, laggy, flight, here it is way out of position and way above the normal tolerances.

The initial INS was pre-aligned. This fact induces a certain degree of intrinsic imprecision but I have never seen such a distortion in the INS after a short flight with absolutely no manoeuvre inducing G>3.
Fixing the INS
There are a number of ways to correct the INS error and they are described in the manual.
I personally recommend the TACAN fix and the Visual in case you have a clear reference point and its precise coordinates (I had acceptable results by using airfields).
I plan to write a more in-depth article about this topic later on.