After some searching I found out that settings of Docker's user interface are stored in %APPDATA%\Docker\settings.json (e.g. C:\Users\olly\AppData\Roaming\Docker), memory settings are defined in memoryMiB property.
The following solved the problem on my environement:
settings.json file using notepad %APPDATA%\Docker\settings.json in the run command prompt (Windows-Key + R)memoryMiB to 1024 (has been 2048 before)
memoryMiBVmMemorysettings.jsonmemoryMiB in Docker versions 19.x and laterVmMemory in Docker versions 18.x and before