Not sure if anyone is still reading this post/thread... but, I'm getting ready to tackle this problem for the two Vantage Vue units I have.
One thing to note: many of the capacitors of this type that I've located on DigiKey, have pretty limited Life specs. For example, the one noted on a previous reply (MAL222091003E3) has a specified lifespan on 1000 hours. That's not a lot! Now I get that that is also at elevated temps, etc., but the fact is, that the typical compact size "supercaps" all have a limited life, from what I can tell.
So, I will probably proceed anyway, with a similar repair, but I'm not surprised that a lot of Davis customers are having this problem, and I'm going to plan to have to replace my "replacement cap" at some time in the future too.
Fun!