More on above bug:
The galaxy map does NOT display correctly after the errors, as far as I can tell.
The star map says the new system (call it "Q") has links to X, Y, and Z.
In systems X and Y, there are JPs now labeled as connecting to Q. These were previously unexplored JPs.
In system Q, the other side of these JPs are visible.
However, there's a JP in system Q that goes to another system I'm familiar with (call it "P"), but it's not Z.
In Z, there's no JP leading to Q.
In P, there's no JP leading to Q.
There is one unexplored JP in each of Q and Z. Ships are en route to check them out now. I'll update again in a few minutes.
Edit 1: the unexplored JP in Z doesn't lead to Q, but to a new system.
Edit 2: transiting the JP from Q to P appears to work (my ship is in P), but does not reveal a JP in P. I will re-survey to see if it is actually there.
Edit 3: the unexplored JP in Q doesn't lead to Z, but to a new system. oddly the system has a name already (same theme as Q, presumably named by the NPR)
In summary:
Star Q was discovered by espionage.
Galaxy map shows links from Q to X and Y, both of which are seen also on star maps, and work fine.
Galaxy map also shows a link between Q and Z, which is not visible on the star map in either system.
Star map in Q shows a JP to P. This JP works, at least one-way, but is not shown on the galaxy map.
When opening or modifying the galaxy map, a bunch of annoying errors occur.
RESOLUTION:
Upon re-survey of star P, the other side of the jump connection to Q was discovered. Now there's no more bug in the galaxy map. The true link from Q to P is now shown, the false link from Q to Z is no longer shown, and the annoying error messages no longer pop up.