Hello rmorin,
What you experience might be the result of a system bug.
Unfortunately, I cannot assess whether this is a bug in your environment, as you did not provide some information about your system version.
For that reason, I would recommend checking LCS for available hotfixes yourself.
Here is a link where I searched for issues around committed costs
fix.lcs.dynamics.com/.../Results;dm=0&v=5_7_4_1_16_15&i=2_1_3_4&ct=1_3_5_4_2_6&ft=1_2_3&cu=&pi=&pm=&pc=&rd=&d=&envId=&permission=&x=19&y=13
You can change/modify this search as you like to find available hotfixes.
Would be great if you could do that and let us know if this helped resolving your issue.
Many thanks and best regards,
Ludwig