strange problem with remembering patches/instruments

I was wondering if anyone has seen this problem and maybe point me in the right direction…

I set up multiple midi tracks and then assign instruments to them using patch scripts. Everything seems to work fine. I then save the project.
When I later open the project some tracks have an issue remembering the instrument selection and appear with a “temp …” as the patch/instrument name. I have to open each track’s patch selector and reselect the the correct instrument.
Anyone seen this behavior before?