This bug effectively ends a game, hard stop, as the players can no longer conquer planets. We have found a workaround but it isn't pretty.
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A save game at the moment just before the invasion has been uploaded to a Google drive directory at "Crash peer on invade last colony.GC3Crusade"
Peer crashes when host invades the last colony owned by one of the last three factions on the board. The previous three factions died without any issues.
Both host and peer are local to each other (in the same room). Both have all of the DLC and both are running version 2.32.
Turn 207
Fleet 5252844 attacking Sanctum in the Iconis system.
Pre-invasion fleet battle
How host dispatches the defending ships does not matter.
Quick invade always fails.
Quick invade with either conventional or information warfare by pressing "start" always results in a defeat for the host with the loss of all legions. Later when the "done" button is clicked the peer will receive a report that the faction was in fact defeated (i.e. removed from the board). If host "guards" or "passes" attacking fleet, then peer crashes. If host moves fleet into the nearest shipyard (or uses up the fleets moves) "turn" comes up and host can pass the turn to the peer. When peer completes her turn either game locks up or one of the players game crashes.
Manual can succeed but peer always crashes.
Manually invading with conventional warfare allows a 2 second window to place all 10 legions. Invading with information warfare allows 5-7 second window to place all 10 legions. If host clicks the "invade" button before the window closes the invasion will be a success, but the peer disconnects. If the host takes too long the peer will disconnect and clicking the invasion button will do nothing. The game will lock up and it will need to be killed.
Work around description: If host can manually invade before the peer disconnects then the host can save the game, restart multiplayer with that save, and continue playing with both host and peer agreeing that the colony was captured.
Addendum: If peer has an invasion failure like this then peer must immediately kill their game after choosing quick invasion. Host will see the invasion succeed and can save game with the colony captured, restart with that save, and both can continue playing.
This assumes the host has "save every turn" selected. Otherwise play from a previous save up to but not including the invasion and have host save before invading.