Clean the drain II
Often there are greasy deposits with a fault in a clogged drain or when it slowly drains off. And since dishwasher powder is quite aggressive against such deposits, the effect seems logical to me.
You need hot water with a temperature of about 65-80 degrees (dishwashers usually work at 65 degrees), and just dishwasher powder. Dissolve the powder in the hot water, add about a tablespoonful to 3-4 L, then pour a good sip into the drain to allow it to take effect, after a few minutes add the whole amount of "lye" in one pour. Possibly. with a mechanical drain cleaner, e.g. Pümpel, help a little bit.
If the drain is completely blocked, first use all the water, then fill in the complete lye. Of course, it is advisable to help a little bit with a puddle so that the lye reaches the clogged area.
Later rinse with a few liters of hot water.