Sounds like the valve isn't plumbed correctly but if it was connected wrong then the functions probably wouldn't work at all. An example, in backwash then nothing would come out the waste line. On the backwash and waste settings you should definitely see activity in the sight glass. In Waste mode do you get good flow out the waste line?
What model filter and valve assembly do you have? Has to be a solution and we'll figure it out.
Al
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