A mixer normally consists of a motor and one or more accessories that can be coupled to it.
The critical point of these appliances is therefore the coupling between the motor and the accessory. Depending on the "philosophy" of the manufacturer, the contact point is made of more or less durable materials. In some cases, it can be seen that the manufacturer has not chosen the most durable or suitable materials for such an important task. It is best to inspect the appliance at the time of purchase and check whether the materials used by the manufacturer for the motor-accessory coupling seems to be up to the task: a tight fit of the components, presence for hard materials (metal over plastic), ...
A blender has to cut, chop, knead and therefore do work that requires considerable effort. If you use materials that are not of the right "hardness", there is a risk that one (or both) of the two components will break easily at the coupling point
If one of the couplings is damaged, you should find out if the manufacturer provides spare parts to replace the broken or worn ones.
Check this article to see how to search for spare parts for your device.
If you can't find spare parts, you can always try to have them made with a 3D printer in a FabLab or specialist shop.
Check this article to see what can be done with 3D printing.
For immersion blenders, there is an affordable solution. Assuming that the mating parts still have enough material to ensure an effective coupling, the solution is to use a very strong glue (preferably two-component) to glue them together. With this solution, the mixer can no longer be disassembled to be washed in the dishwasher, but can continue to be used. It is conceivable to use this solution for food processors too, but this means that only one accessory can be used and the others must be discarded.
This is a choice to be made if the alternative is to throw everything away!
General repair tips :
Caution
This tutorial was written by Repair Together - the network of Repair Cafés in Wallonia and Brussels (Belgium)
With this project, we try to create relevant guidelines on a product category and frequent faults level. The exercise is led by different repair networks, but our content can only grow and improve thanks to your help.