Rebrickable Help Guide: Fixing MOC Inventory Errors

Fixing MOC Inventory Errors

There are several types of errors that can show up in inventories when you are submitting a MOC. This guide will explain what they mean and how to resolve them.

Rebrickable also now regularly scans published MOCs that are alternate builds looking for inventory errors and will tell you in a banner on the homepage if your MOCs contain errors. These can be corrected in similar ways to MOCs in progress. If you do not correct these errors the MOC will stop being displayed as an alternate. To restore your MOC's alternate status, simply fix the errors and request a rescan,

These types of errors are usually caused by mold varients of parts in the source set. The set inventory may have been updated since your MOC was published to correct errors, or an extra version of the inventory could have been added. To specify a specific inventory version for your MOC, list the set number with inventory at the end like this 31109-1:v1. If no version is specified, the inventory will default to the most recent version which may change over time.

When you click investigate and resolve it will take you to https://rebrickable.com/users/username/mocs/errors/ which shows a list of the problematic MOCs and gives an option to rescan your MOCs. Note that MOCs are only scanned once a week and the table is not updated automatically when you fix them. Only MOCs submitted in the last two years are scanned.

Missing Parts

If your MOC is an alternate build of a LEGO Set, all the parts in the MOC must exist in the parent set you have specified. Rebrickable automatically does a Build calculation in this scenario and highlights parts that do not match.

During the submission phase, the highlighting of alternate builds is based on the parts existing in the parent set. Once the MOC is approved (or your MOC is not an alternate build) the highlighing of parts is based on the parts existing in your buildable LEGO collection.

Parts colored red do not exist in the source set, and parts colored orange do not have enough quantity in the source set. All parts colored orange or red will need editing to remove the error. Do so by clicking the part so you see the popup details page. If the MOC is in progress Rebrickable will attempt to show suggested parts based on similar parts in the parent set. Simply click on one of the suggested parts and Save. Clicking a suggested part will update the part number and color fields to that part. If no suggestions are shown, you will need to manually edit the part number, color and/or quantity.

Another way to identify parts that are missing is to use a build calculation or the compare sets tool. This is especially useful when fixing MOCs that are already published as the colour shading will be reflecting if you have the parts in your buildable collection, rather than if they exist in the source set. Any MOCs with inventory errors will prompt you to use a build calculation or the compare tool when viewing the inventory.

In the below example I have used the compare tool and found there is one part in my MOC which doesn't exist in the donor set, this is shown on the left hand side. You can see a similar part on the right which is a mold varient of the first, it is present in the donor set but not yet used in my MOC. So to solve the error I need to replace part 30350b with part 65886 in my MOC inventory.

Spare parts are not included by the compare sets tool. Using spare parts in a MOC inventory is not considered an inventory error, however any spares used will show up on the left hand side when using the compare tool.

Click on the left hand side part, go to the Edit this Inventory Part tab, and then amend the part number and click save. Continue to do this for all parts on the left hand side (which are not spare parts).

Alternatively, if you click show Build Results this will run a build calculation with special settings that will exclude all of your buildable collection, but add a copy of the source set. This will correctly include spare parts in the calculation, but will only show the missing parts, and you will need to check the set inventory for which version is needed as a replacement.

Unknown Colors

Parts with the Unknown color usually occur when importing from a 3D file such as LEGO Digital Designer. In some cases, the colors used in the program are not configured in Rebrickable and so the Unknown Color is used instead. If you encounter these, please submit them as a Bug in the Forums, preferrably with your 3D file attached. That way, we can add a mapping for that color and future imports will work correctly.

Fix these errors by simply editing the part and picking the correct color, then Save.

Part Errors

These errors occur on parts that have not been used in any official LEGO set inventories, according to the Rebrickable database. Often the reason is because there are several part numbers for the same physical part - perhaps with slight molding differences, or maybe just duplication. Sometimes it is because the part is normally inventoried as an assembled part with multiple sub-parts.

Fix these errors by editing the part and changing the part number to the correct one.

Color Errors

If the part is using a color that has not been used in any official LEGO set inventories, you will get the Color Error. It could be because the the color imported incorrectly, or because the part is actually the wrong one.

Fix these errors by editing the part and changing the color to a correct one.

Last modified March 17, 2025 by icedragonj

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HELP - Fixing MOC Inventory Errors

Fixing MOC Inventory Errors

Missing Parts

Unknown Colors

Part Errors

Color Errors

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