There should only be one bug per thread as per https://forums.flightsimulator.com/t/read-first-about-the-instruments-category/320472
However, the first point you raise is probably answered in this thread https://forums.flightsimulator.com/t/oat-of-248-c-at-fl285-impacts-negatively-on-aircraft-performance-and-autopilot-function/478029
For the second issue re. the ILS, two things to suggest,
- Check the correct frequency is being used
- Check that the LS button under the barometer settings is selected “on”
I have not seen any issues withe the ILS if both these steps are taken.