Are u sure that the water is still not in the reservior? After the partial brew, CAREFULLY check / empty the reservior for the missing water. If it's still there, then u probably have a clogged perculator hole at the bottom of the reservior.

I just figured out how to correct a slow / partial brew problem for a 4 cup Mr. Coffee that left the water in the reservior...I have been using paper towels and napkins to dry the reservior and cover after use, and apparently bits 'n pieces of paper clogged the tiny little hole at the bottom of the reservior that the hot water perculates through

Multiple vinegar/CLK flushes may eventually desolve this paper clot, but I used my vacuum cleaner with slat attachment to **** the paper clot out.