The sort of issue is often the .dp file. The dp calls out the bomb load and the number of bombs the aircraft carries.
The gunstation section should have a line like this:
Then the number of bombs needs to be listed after the individual guns are listed like this:
[GUNSTATIONS]
; 0 Chin Gun
gunstation.0=0,51,1,0.08,747,2,0.01,1000,1,100,1d1*8,0,-0.28,5.509,0,0,0,-45,30,45,-45,0.37
; 1 Upper Gun
gunstation.1=0,52,1,0.08,747,2,0.01,1000,1,40,1d1*12,0,1.7,-5.3,-45,0,180,-90,90,45,-45,0.37
; 2 bombs
gunstation.2 (the sequential station number)=3,21,8,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
Then the number of bombs needs to be called out next like this:
[guns.0]
gun.0=600,0,0,0,0,0,1,600
[guns.1]
gun.0=600,0,0,0,0,0,1,600
[guns.2] (the sequential station number)
gun.0=16,0,0,0,0,0,0,0 (the number in red is the number of bombs carried)
If the gunstation section is listed but the [guns] number is missing or not listed. the bombs disappear when dropped.
I loaded up the YAS Mk VC (ZP-X) and accompanying weapons files to see if the problem duplicated. It didn't. The bombs show up and drop except for the combination 250 lb and 500lb load. The dp is messed up in how it is written and does not work as intended. BUT - the bombs do show up.
I couldn't duplicate what you are describing so, I would suggest re-downloading the file (which includes the weapons pack) and reloading them and see if the problem persists. It might be something was corrupted or missing. ??