I have completed all three games and Insanity 3 and Paramore 3 not unlocking Ps5.
So I also had this issue with Insanity 3 not unlocking after beating ME3 a day after the patch. I tried a few different times to replay the end to no avail. Today I remembered I had saves on ME1 at the Saren fight and on ME2 near the end of the Collector base. I started with ME1 and killed Saren again, checked to see that the in-game achievement tracker now showed Insanity 1 & 2 as complete. I started up ME2 and beat it, and voila, Insanity 3 popped.
So to anyone at their wits end, maybe this could help you get this done and out of the way.
