This is the most common case of a malfunction in a weighing system and could be due to a calibration error or a mechanical problem.
Here are the tests you can run to identify the problem and find the solution:
Load several weights that are proportional to each other and check whether the error is constant.
For example: if you load 50 kg on the scale and the indicator gives you a value of 55 kg, try unloading it and reloading it first with 100 kg and then with 200 kg. If the error stays proportional, i.e. instead of 100 kg the indicator shows 110 kg and instead of 200 kg it shows 220 kg, it means that the system does not have a mechanical problem.
In this case, simply perform the calibration again, following the procedures in the manual.
If, on the other hand, the error displayed is random, so not proportional, then the problem is mechanical or it regards assembly.
Immediately verify the mechanical installation of the load cells, mounting accessories and structural components (e.g. pipes, silo legs, cylinders, etc.).