Is that due to pilot error, weapons issues, or bad instructions from CAC or ground forces?
The fact that A-10s have the most? That is due to them having a lot of exposure more than most airplanes had, at least at the time. And the causes were mis-ID of targets, one was an AGM-65 that went stupid on launch, but many were errors from air unfortunately.
Wasn't the first, won't be the last.
B-1, B-52, A-10, F-16......all are tools in the CAS toolbox, used for specific purposes or situations, OR if nothing else is available.
Want to drop tonnage in support of friendlies, but aren't danger close? A B-1 does just fine. A-10 would do fine, but it doesn't carry the load the B-1 can. So if hitting friendlies is a lowered probability with the attack you're doing, a B-1 is fine.
Conversely, when danger close, you want the A-10....or even a trained/experienced pilot in an F-16; something that can get low and see the battlefield (A-10 better than F-16, mind you...but the F-16 can get low if need be); and you sacrifice ordnance tonnage for accuracy. Accuracy which is critical in this situation.
So, different tools for different situations.
AC-130 is great too. But it also has its limits as when that tool can be used. As does any aircraft.