Rendezvous Target Ship Orbit Changing When Under 2250m Separation

[Gernrat]

I have returned to playing KSP after a couple year break and have had an issue when building a space station. The station has a low eccentricity and inclination 225km orbit. To add new parts, I launch from KSC at about 70 degree pitch with the station a few minutes from passing overhead. With an apoapsis just over 225km I have a pass at about 3km. Once up there, I burn prograde and work toward rendezvous. 

When the station loads at about 2250m, I have about 80m/s closing velocity. As the station loads, the game skips for a second and my closing velocity is dropped to about 1.2m/s. When checking the map, my orbit is now matched with the target, and we are both suborbital. 

I thought that maybe the game was thinking my exhaust was impacting the station from absurdly far away, so I tried again and made sure not to point my rear at the station with the same result. 

Has anyone heard of this happening?

I know more info will be requested and will get mod list and pc specs up when I get home from work. I'm running this on a 6 year old laptop and know well that's a problem, but I'm not sure if it causing this particular issue.