Since Version 24.3, user cannot insert / modify lines within Assembly BOM with Quantity Per is zero or empty.

You get an error message : "Quantity per must have a value in BOM Component: Parent Item No...."

In the case you are using Copy from Assembly BOM feature to fulfill Service Item component list, the quantity might be zero to let the user fulfill actual quantity and not apply by default the theoretical quantity.

"ServComponent-Copy from BOM"(CodeUnit 5921).OnRun(Trigger) line 3 - Base Application by Microsoft

"Service Item Component List"(Page 5986)."&Copy from BOM - OnAction"(Trigger) line 3 - Base Application by Microsoft

In my opinion, this is a regression.