That means that the PinMechSound command is using a fp_item that doesn't exist on that table.
Each PinMechSound command must be updated to reflect the actual fp_item names used on that specific table.
If the user enabled DOF or PUP_SSF, then the PinMechSound command will no longer be using Playsound (which doesn't use the fp_item). It will look for that fp_item specified in the command, and if it doesn't exist (has the wrong name, etc), then you may only get that error when DOF or PUP_SSF are enabled.
This is why I say that if you aren't sure how to properly use PinMechSound, or you don't want to worry about supporting it, or getting this kind of error, then you must disable DOF and PUP_SSF, and make a note to keep them disabled, as they are not supported on this table, etc.
Note, how the PinMechSound commands's fp_item matches the Trigger, which has an X / Y position and a name that matches that FP can reference and find on this table.
If FP can't find what is shown on the fp_item section of the command, then you will get an error when DOF or PUP are enabled.
Not every table uses the same names for similar table items, so you must check them to be sure they are correct.