'Drive System Optimization' Research only gives benefit once

Version 1.05

In this endgame that I am playing, I have already researched 'Drive System Optimization' but it continues to appear. So I've researched it 2-3 times but it only has increased the movement the first time I researched it. You can confirm I've researched it by looking at my ships. Replicate by selecting 'Drive System Optimization', research it again and see that my ships don't get faster.

 

Here is the save game:

https://1drv.ms/u/s!Ah4pxQwvINgZ91Eb6kqD39xeen3Q?e=NSPVmr