Picking for a SO

We are a month in to turning our WMS system on. When picking for a SO the majority of our lines are soft committed and the system will create the suggestion. However, we do hard commit partial lots sometimes. It seems like when we hard commit a lot, the suggestion will error out and give us a 3448 quantity invalid error. If we look at availability it shows we have enough. If we use the manual planner it goes through no problem. It seems like we just get the error when we approve the