Default Learjet 45 autopilot

OK, here is the story:I am on final, decision height reached (200 feet), turn autopilot off, slightly increase thrust, trim a little bit, ready to touchdown, but the nose is getting higher, higher, higher... Moving elevator manually does nothing.OK, Missed Approach, fly standard pattern and again, DH set to 100 feet (no obstacles), and the same story. The third approach was by autopilot almost to TDZ. I have landed safetly, but what I have noticed, is Altitude Hold is still active (i set it to 100ft with -200fpm, TDZ was 19ft). Is it my fault, or the Learjet 45 from Microsoft is buggy?