Some time ago, I described a problem with the DEBUG Interface and a solution was provided but I cannot find the answer.
The problem is that the Basic stamp will stop processing a program for a reason that is not well understood. When the DEBUG is used to display computations made in the Basic program on the computer screen...there will come a time when the program will halt. The stoppage has been random occurring from days to months but it will eventually stop the process.
The solution was to do something to the Rx or Tx lines but I don't recall.
The same situation occurs on the Propeller interface to the computer screen. If the interface is disconnected, the programs run fine but my system design requires monitoring data sent to the computer screen.