The autopilot nav lock on my aircraft has worked for some time now, but within the last several weeks, it will no longer engage. Playing around with different options, I finally got it to work again, but my solution is far from ideal. In order to get the nav lock to work, I displayed Simvar Watcher to verify that the variable "GPS DRIVES NAV1" is set to zero and then I temporarily repurposed another switch to first set that variable to 1. After verifying that the variable is 1, I hit the switch again to set it back to zero. After doing this, the nav lock works as expected for the remainder of the flight. I am not sure what is causing this. I looked through my systems.cfg and could not find any setting under autopilot that I thought would effect this nor do I have any other code interfering with this. Was there a recent change in how the nav lock works that I missed? I'm at a loss, anyone have any ideas?