I pulled out my NXT recently to tinker around with it. After reconstructing one of the suggested builds, I was writing a small program for it. About halfway through, I needed to leave my work, so I tried to save the file, but I was unable to. I received the following completely straightforward and not confusing error message:

error message

The text of the error message reads

Insane object at BHDP+3C18 in "Arm4Caleb.rbt": {graphics } (0x80): Loop Tunnel DCO )

with Arm4Caleb.rbt being the name of the file. I have failed to find what this error message may be referring to.

I also attempted to save a blank NXT program file; this was successful, leading me to believe that there was something wrong with my particular program. Consequently, I attach an image of the NXT program (I can't post the file because I can't save it):


The program is in collapsed mode so that I can screenshot it; the alternate decision for the largest switch "box" is a use of the C motor; the alternate decision for the medium box is a use of the C motor in the opposite direction; the alternate decision for the smallest box is doing nothing.

It's been a while since I've tried this visual coding stuff; I suppose I have an error somewhere in here? I'm not sure why it would prevent me from at least saving the file, though.

1 Answer 1


Apparently, all that I was missing was a STOP block at the end of the thread. Hopefully my oversight helps future users.

The STOP block looks like so:

enter image description here

  • Do you happen to have a picture of correct program with a "STOP" block to include in your answer?
    – Alex
    May 10, 2020 at 16:42
  • 1
    @Alex do you think a picture of just the STOP block would work?
    – Brandon_J
    May 10, 2020 at 16:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.