Replacing a rail signal which has a circuit wire connection with a chain signal works as expected.
(I guess it is kept in the undo buffer as a deconstruct and construct order)
Undoing that action marks the rail signal for deconstruction and places a ghost of a rail signal.
Then my construction bots remove the chain signal (thus deleting the wire connection) and place a rail signal, which now of course doesn't have any circuit wire connected to it.
It'd be better to mark the signal to be upgraded to the other type instead, such that the wire connections are kept upon undoing the replacement.
(I guess keeping track of an upgrade action in the undo buffer? Instead of the deconstruct & construct pair mentioned above)
That is essentially what happened. I did not deconstruct the signal and place another one, I manually upgraded it by replacing it.
