Working on Rev. 557.
If I create a new simple circuit, save as .sim1 and then simulate it, it works as expected:
If I then close the program, reopen it and reopen saved .sim1 file, the bus line does not seem to transmit any more:
Things get back to normal if I delete the bus line (green line) and recreate it. However, after saving, closing and re-opening problem re-appears, as expected.