We had a problem with the plumbing and housekeeping on the Zaandam. In our case the ship was full and we had limited use of the head. There were about 10-15 cabins that were having the same problem. We were told that someone, probably from the last cruise put something in the toilet that they shouldn't have. It took them all week to get it fixed.
We made our complaint onboard, then later wrote them a nice letter.
We are going to give HAL another try, this time on the Volendam. They did adjust our bill when we were onboard, and again with our letter.
I think it is only fair to give them a second chance.