The issue here is a semi duping bug.  Seems to happen when swapping construct type while they have items (weapons or modules) equipped.  When you get the inventory full message you will find that there is an item that is both on the construct and also in the inventory list.  You can work around it by moving the duped item onto another construct or vendoring/salvaging it.

We correct this issue as soon as possible, thanks for your report! 

We are working on the final solution but thanks for the useful workaround! It may help to someone for the time being.