After Pregrinder clinker get free flowing and when material column above hopper will be less it tendency tpo flush from weigh feeder.

In between weigh feeder and hopper there must be a rotary feeder and which will resolve the flusshing issue.

Maihar cement same issue has been resolve by Schenck.

The pre gorund material is almost 90 % through 1mm .It is very fine .To regualte the feed to weigh feeder we needto install prefeeder and provide wider width belt to avoid spillage  and  space for settling the dusty clinker  to ensure weighing accurracy .The problem can be better addressed to weigh feeder suppliers for accurate solution.