Bug description: Even after successfully invading and occupying the Deneb system, the invasion option remains in subsequent turns. Unfortunately, I've deleted all files between turn 103 (before occupation) and turn 122 (after occupation). But I hope my description and uploaded saved files will suffice.

In turn 103 screenshot 1 below, you see that Sophons still occupy the Deneb system (before my invasion of that system). In turn 103 screenshot 2, the Sophons are at war with Riftborn.

In turn 122 screenshot 1 below, I have already successfully invaded and occupied the Deneb system before this turn. This can be seen by the improvement being currently built. By this time, I had a truce with the Sophons but was at war with Riftborn. This is the part where my memory gets a little hazy because it happened so fast and I lost the save. When I first invaded Deneb, it was under Sophon control (I was at war with them aka the blue guys earlier). After several invasion attempts on Deneb, the defending Sophons proposed a truce and I accepted. This is when the first bug supposedly happened because the defenders (blue guys) suddenly disappeared from the system, which now has an orange ring (the competing invader's aka Riftborn color)! But the system is completely uninhabited by the competing invader's pop. This part is hazy because I don't remember seeing any competing invader fleet on this system but it happened so fast.

Weirder still is that after all the Sophon pop was wiped out (perhaps due to bombing), the pop remained at 0 and there's no sign the system will ever be inhabited.

In turn 122 screenshot 2 below, I was also still able to click the invasion button and the invasion screen popped up even though I'm already occupying the system and building improvements on it! Even after each "successful invasion", I'm still able to repeat this process an unlimited number of times on the same turn.

The screenshot below gives a closer view of the occupied system on turn 122.

Steps to Reproduce: As mentioned, my memory is a little hazy between turns 103 and 122 but I hope the bug description is clear enough. This is what I think happened:
1. As mentioned, this step is just my theory of what happened because things happened so fast. Invade enemy system. The system cannot be captured in one turn and requires several invasion attempts over a few turns. Have a third faction's fleet (aka competing invader) also invading the same system. However, the primary invasion fleet (which is mine) is the one that invaded the system first and is expected to occupy the system if the invasion succeeds. End turn.

2. At the start of the next turn, select the bomb invasion option and repeat this over the next few turns until the next step happens.

3. At the start of the new turn, have the defenders propose a truce and accept. This is when the first bug supposedly happened because the defenders (blue guys) suddenly disappeared from the system, which now has an orange ring (the competing invader's color)! But the system is completely uninhabited by the competing invader's pop. Continue blockading the system.
4. The orange competing invader declares closed borders with you, but don't move your fleet anyway and continue blockading the system.

5. Wait a few turns. Then declare war on the competing invader. Invade the blockaded system (which still has zero pop), then occupy it. See if the system ring color immediately changes to that of your invasion fleet or remains that of the competing invader's. If it's the latter, this is the second bug.
6. On the same turn as the successful invasion, try to build improvements on the captured system to see if that's possible. End turn.
7. Select the primary invasion fleet and see if you can still repeatedly "invade" the occupied system multiple times on the same turn. If the invasion button isn't greyed out, it's the third bug.

Reproducibility: 1/5

Expected Behavior: I think the invasion mechanic is supposed to correctly identify the primary invasion fleet so that at the start of the next turn (when the invasion takes several turns to succeed), the primary invasion fleet will occupy the system assuming it has weakened the defenders successfully. This should happen even if a competing invader fleet subsequently entered the same system while the primary invasion fleet's invasion is still in progress over several turns. Once successfully occupying the system, the system's ring color should change to that of the primary invasion fleet, not that of the competing invader fleet. If the primary invader is disrupted by a truce request and accepts, there should be a clear message that the competing invader has captured the system instead (if that actually happened) because the third party is still at war with the defenders. 

Also, the invasion button should be greyed out after the system has been captured (under these conditions).

Version: Latest

For some unknown reason, I'm unable to upload the diagnostics file here. But attached are my save files for turns 103 ("4" zip file) and 122 ("AutoSave 121" zip file).

4.zip

AutoSave 121.zip

Thanks for the help!