Do these cover repair quotes seem reasonable?

[Involute]

We have a rectangular in-ground pool with an integrated cover that rolls up via a hydraulic motor into a vault at one end. The rolling up stopped the other day and the maintenance company initially said the contactor blocks inside the hydraulic powerpack needed to be replaced. Later, they said that, actually, the whole powerpack had to be replaced since the contactor blocks will just short out (after some indeterminate time less than a year) due to whatever the problem is in the powerpack. So, they want $4K to replace the powerpack, or $900 to replace just the contactor blocks, though the blocks would be unwarranted since they could short out at any time. Does any of this make sense? The powerpack is about nine years old.

[Teapot1]

Without more information or photos I couldn't possibly answer.
What is the cause of contactor blocks shorting, water ingress? Is that due to gasket failure?

[Denniswiseman]

Have you spoken to the manufacturer

[Involute]

Here's a photo of the powerpack. I don't know what's causing the contactor failure. I haven't spoken to the manufacturer. Which one should I speak to, the manufacturer of the powerpack or of the pool cover system? Another tech I spoke to suggests I just add some more hydraulic fluid. The level is 2" - 3" below the top of the tank. I'm happy to try, but neither he nor I know what's in there now, and I'm leery of mixing different types. He said automatic transmission fluid would be fine. Any thoughts on that?

[Teapot1]

Check with the powerpack manufacturers