Is that a skimmer plate for winterizing the pool? Do you not lower the water level to below the skimmer before closing your pool?
We lower the water level to close the pool and don't use a skimmer plate. We did the first couple of winters but we had to remove the skimmer and screw on the plate. Now we use some of the winter water and spring rains to start bringing up the water level before opening.
Sorry, I know I'm not answering your question. But its a thought for next year.
You need to keep the cover drained so it doesn't push the water high enough to get to the return or skimmer. The whole reason to drain the level before putting a cover on is to keep ice away from the skimmer and return. If you just let water pool on the cover, pushing the pool water back up to them that makes the entire thing pointless.
Also that valve on the skimmer needs to be left open to keep water out of the housing or ice could break it. Rain, snow melting etc all will end up inside the skimmer and I honestly don't know how that valve or skimmer isn't cracked at this point.