Kuva Siphon Assassination not dropping Warframe parts

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Hypothesis:

• Doing Assassination missions with the Kuva Siphon modifier(?) will prevent Warframe part blueprints from dropping.

Data points:

• Did a Themisto Kuva mission and had no Valkyr part drop at the end.
• Merrow Kuva Flood, no Saryn part.
• I also found this related report:

 

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Update 29.2.4

• Kuva Siphon and Kuva Flood on Iliad dropped Mag parts.

This issue might've been fixed somewhere in the 29.2.x series. Will have to check some more nodes though.

[(PSN)H-Refr]

I just did Lech Krill assassination on Mars with Kuva Siphon modifier. He didn’t drop Excalibur part. 

It’s on PS4 so we may be behind on bug fixes.

Edit: just did The Sergeant kuva siphon, got a Mag part as the mission reward. So i seems not all assassination missions are affected.

[Y0rg0]

I did a few kuva-modified Lephantis assassinations and also a nightmare version of that mission, no nekros parts dropped in any of those missions!
Then killed him in normal mission mode - always nekros drops...

Happened to me just a few days ago - so (if not intended) this bug is still in...

edit: on PC

[JustSomeGarbage]

Just did Kuva Siphon Hades, Pluto assassination (Ambulas). You're supposed to get a Trinity part and 10 Animo Beacons back as the normal mission reward. I didn't get either one, but I still had to spend 20 Animo Beacons to do the mission.

I feel like I should get the Trinity part and the beacons back, or I should not have had to spend 20 beacons to do the Kuva Siphon. This seems to be an issue on all missions that require some kind of key - Hades, the Sedna arena missions, and maybe Mutalist Alad V (haven't seen a Kuva Siphon/Flood on that node though). I didn't farm those beacons so I could get a little Kuva, I farmed them so I could get all the Trinity parts.

I did a little testing. It appears that the mission reward drop table is replaced with the Requiem relic drop table. Interestingly, you DON'T have to kill the Kuva Siphon in order to get the relic. In fact, if you fail the Kuva Siphon but finish the mission you can still get the relic (but you won't get any Kuva, since that drop is associated with the siphon itself). The best solution is probably to remove the key requirements for Kuva missions.