Have to check thanksThe wear ring is probably shot. How much gap between impeller and ring?
ThanksAD comment above there, is likely the deal…but some of these have had a quarter turn valve fitted in line to the outlet. Just so you can turn it off, should it be an annoyance to some. Maybe yours has had one fitted too…and it’s half closed perhaps. Just an out the box idea…but odds on, @alldodge is spot on. Or the pipe to the outlet is compromised.