When carrying multiple types of bombs, I've noticed that switching between them using the 'cycle weapon' bind results in the newly selected bombs to have their fuses reset to 'safe' mode. Switching back to the first set of bombs, then cycling weapons again will usually fix this issue (the bombs will show the correct fuse setting).
This appears to be more than just a bug in the display. Upon dropping bombs I armed earlier, but had shown as being in 'safe' mode due to this bug, I found they didn't detonate on the target.
Example for recreation:
1. Arm the aircraft with 2x Mk 82 unguided bombs on the inner pylons and 2x Mk 20s on the outer pylons (it can happen with any 2 types as far as I can tell, so this is just an example)
2. Take off, then flip the master arm on and change the fuses to N+T for one bomb type (or N or T, doesn't matter really)
3. Cycle to the next bomb type and set the fuses for them
4. Cycle from the now armed bombs you currently have selected to the unselected bombs that you armed earlier
5. Newly selected bombs often show their fuses as 'safe', meaning they will not detonate if you drop them
6. Cycling back and forth between your bombs a few times causes their fuses to be shown correctly (ie N+T instead of safe)