Shipments to Amazon – SC doesn’t help with stuck shipments, any advice to contact FCs directly?

We typically have shipments that have been in receiving for months and it’s very frustrating to contact SC support and they just say “wait till it’s available for reconciliation”. The reconciliation/investigation date keeps getting pushed back every week and meanwhile these shipments are stuck for months. Currently have 3 coming up on the 3 month mark. There’s been no movement since the week after they checked in so it’s frustrating to not be able to question anyone about it. Does anyone have advice on who they contact when they have this issue? Is there any warehouse support? Any way to contact the FCs directly? Our rep will help if they haven’t checked in but will wash their hands of it if even 1 item has been received.

Thanks in advance.