Cannot find inventory items with underscore with Api

I have an Inventory with underscore eg. TEST_1 with the same description.

If i make a request with ?$filter=InventoryId eq ‘TEST_1’ it cannot find it but it can find it with  ?$filter=Description eq ‘TEST_1’.

I CAN also find with  ?$filter=InventoryId eq ‘TEST_1’ it but when I query a GI with Odata, but not with Rest API.

This is the case for all items with underscore, any ideas? My segmented keys for items are question marks and not underscores.