I have no door on my skimmer. I know what you are talking about but this is a different design that does not have one.
The pressure is normal....but......when I complained about what I thought was a problem with the pump sucking, the contractor placed flow restriction caps on all the pool inlets. The flow from those are very strong, its just that I dont notice things easily flowing to the skimmer. I thought there would be a fairly nice current into the skimmer when it was 100%. Perhaps that is not the case? But there is definitely some blockage from a concrete blob in the intake tube as it turns in the skimmer.
Filter PSI under normal operation is 12PSI when clean.
The "current" is important for me because we get a lot of small flies overnight on the surface of the pool and I want to skim it off as soon as possible in the morning. This being our first spring/summer, I dont know if this is going to be the norm, or if its some kind of temporary swarming/mating, as it just started this week when the temps have risen to the 70s overnight.