Sand im Getriebe
a spanner in the works; a disruption in an otherwise smooth process
Origin
The image comes from machinery: sand between the gears destroys the lubrication and jams the mechanism, so that a machine - figuratively an organisation or process - stalls. The expression became common in the first half of the 20th century.
Building blocks
Words in this expression
Examples
Die ständigen Streitereien im waren im des Projekts.
The constant quarrels in the team were a spanner in the works of the project.