I appear to still be losing fluid, and I wonder if it has anything to do with the odd behavior of fluid handling by the solar tower once the molten sodium fluid level drops below what looks like 15mB of fluid. I've recorded a brief video showing the behavior as shown in WAILA.
Edit: Currently testing to see if keeping the fluid levels high on both the cold and hot side eliminates the fluid loss, which should verify if the below-threshold behavior of the solar tower is the cause or not.
Edit 2: Fluid loss is still occurring, so I'm guessing it's not the low fluid behavior of the solar tower. I've also been running the system exclusively at daytime so I don't think it's the varying input power on the machinery involved in the sodium cycling either.
Edit 3: If anyone can think of any other things to test for fluid loss, do let me know and I'll test it.
For now, I'm just going to be using creative portable tanks in place of my reservoirs until the issue causing the fluid loss is fixed.
Testing a configuration with a reservoir on only the cold side.
Edit 4: A small refactor with large implications, the reservoirs on cold and hot side now function purely as a "pressure relief", rather than an inline tank. This allows the total volume of fluid throughout the cold and hot side cycle to fluctuate, the excess of which going into the tank with the servos and retrievers serving effectively as pressure regulators. Probably easier to understand with the picture. Hopefully this results in no net loss of fluid - I'll find out with time.