Earlier this year I encountered this bug while trying to complete the gene stamp collection. I refused to run the missions twice and wanted to complete it in one go no matter the time it would take, it should be possible.
I have seen this a few times. Now there is no longer a need to run the missions anymore for me, so I decided to finally report it, since I won't be able to verify if it ever gets fixed.
Also if nobody has reported it the collection of genestamps has been terrible since the weapon locations take up the gene stamp location, and I know this since I have counted like 12-15 dead Grineer in mission but only 3-4 gene stamps sometimes and then the 5 weapon swaps. This is all from memory so numbers are off, but I did run the 100% full maps on these missions and verified everything in the enemy radar.
I have 100% completed the Kahl mission countless times like here: